Re: Locker Information Links
More on lockers and differentials:
[B]The Open Diff.[/B]
[IMG]http://www.ebroadcast.com.au/ecars/A/PiCs37/diff.jpg[/IMG] The heart of the differential is the diff' centre (right). It rotates, driven through the crown wheel (gear) by an input shaft and pinion gear. Internally it carries two or four planet-gears and two side-gears. These planet-gears drive the side-gears which are connected to the half-shafts which drive the wheels. When driving straight ahead, the planet-gears do not rotate relative to the diff' centre, and the centre, the side-gears, half-shafts and wheels all rotate at the same speed.
If one wheel needs to rotate [I]more[/I] quickly, it can do so, overtaking the centre by rotating the planet-gears in the centre which makes the other wheel rotate [I]less[/I] quickly. In fact the centre always rotates at the [I]average[/I] speed of the wheels, C=(left+right)/2, which is why it can be used to add inputs in mechanical analogue computers. If the centre is stationary, a wheel can still rotate provided that the opposite wheel rotates in the opposite direction. For this reason it is [I]especially[/I] important that vehicles having a transmission hand-brake be securely chocked when a rear wheel is jacked up.
The differential action of these `open differentials' is essential to stop tyres scrubbing, to reduce transmission loads, and to reduce understeer during normal cornering.
The torque carried to the wheels by the two half-shafts must be equal because they are balanced through the planet-gears. This means that if one wheel looses grip, due to slippery ground or through being in the air, the other wheel effectively losses all input torque and cannot propel the vehicle. A 2WD with an open diff' looses traction if just one driving wheel does. A full-time 4WD, with an (unlocked) open centre-diff' looses traction if any one wheel does. A vehicle with 4WD engaged (or with a centre-diff' locked) and with open axle diff's looses traction if one wheel on [I]each[/I] axle looses traction. This can happen if the vehicle gets crossed-up by being supported on diagonally opposite wheels, or if one side is on slippery ground, for example.
Coefficients of frictions from [1]:
wet ice 0.1; packed snow 0.3; mud 0.4; loose gravel 0.5; good road 0.9.
[B]Diff' Locks.[/B]
[IMG]http://www.ebroadcast.com.au/ecars/A/PiCs37/Diff.locks.maxidrv.jpg[/IMG] The differential action while essential for normal driving can leave a 4WD stuck with just two spinning wheels. The most obvious cure is a diff' lock. This is a dog-clutch of some kind that prevents the differential action when it is engaged. The most common arrangement is a dog clutch on one half-shaft, which can lock it to the diff' centre. This also locks the other half-shaft, indirectly, via the planet-gears. The dog clutch is engaged by some sort of external actuator. This system is mechanically simple. The Maxi-Drive (right) is of this type.
Many full-time 4WD vehicles use a (centre) diff' lock of this kind in the transfer-case, although we then have front and rear transfer-case output shafts in place of axle half-shafts. It is important to note that a centre-diff' lock does not lock the axle diff's.
The Roberts (now ARB) diff' lock is internal to the diff' centre. A dog clutch locks the side-gears to the centre. The clutch is engaged by an annular piston driven by compressed air and is disengaged by springs. The problem is getting the air to the piston inside the rotating centre! The air is carried in from outside through a rotating seal, similar to devices used to inflate tyres on the move on some very heavy duty offroad vehicles and some military vehicles. The result is ingenious but complex. A disadvantage of the design is that the "warning light" shows when the diff' is [I]intended[/I] to be locked not when it is [I]actually[/I] locked.
[IMG]http://www.ebroadcast.com.au/ecars/A/PiCs37/Diff.locks.mcnamara.jpg[/IMG] The simplest diff' lock of all is made by McNamara. A lengthened half-shaft can be slid in or out by a distance of a couple of inches by means of a spring and bolt on the modified wheel hub (right). The half-shafts are splined to the diff' side-gears, and also to the hub driving plates on fully-floating hubs as used on most serious 4WDs. When the lengthened half-shaft is moved inwards, it protrudes through the side-gear and engages with splines in a modified `spider' that carries the four planet-gears within the diff' centre. This locks the half-shaft to the centre and hence locks the diff'. It is necessary to stop and operate this diff' lock with a spanner, and it can only be fitted to the rear axle of a vehicle with fully-floating axles, but it is very simple which is no bad thing.
Below, an in-cab-operated McNamara diff' lock for a Toyota Landcruiser (70/80/100 - series) on a display jig at the [URL="http://www.ebroadcast.com.au/ecars/News/1999/990221.FieldDay.html"]4WD Field Day[/URL]. Price is $1450 per unit, fitting about $500 ($au 1999).
[IMG]http://www.ebroadcast.com.au/ecars/A/PiCs37/Diff.locks.mcnamara4.jpg[/IMG]
This type was initially developed for Rover differentials and used in competition on a [URL="http://www.ebroadcast.com.au/ecars/LandRover/RR1/1981.html"]Range Rover[/URL] in the [I]Malaysian Rainforest Challenge[/I], winning in 1998. The original alloy housing tended to crack as the [I]front[/I] axle twisted when cross-axled, but current iron castings are stronger.
The locking mechanism operates on the (large diameter) side gears, but the actuator is mounted on the diff' housing and so does not need complex seals nor a high pressure air supply.
[IMG]http://www.ebroadcast.com.au/ecars/PiCs37/1x1tr.gif[/IMG]
In some ways a diff' lock is the ultimate traction device. All wheels revolve at the same speed when engaged. A vehicle with locks on all axles has traction if just one wheel does. Unfortunately a diff' lock is on or off; there is no in-between. This can make the vehicle understeer (tend to go straight ahead in corners) or veer suddenly sideways if one side looses traction, on ice say. It also means that all of the engine's torque, amplified by low-range, can go through one half-shaft and wheel. The components had better be able to stand the strain. Some diff' locks come with strengthened half-shafts and other components for this reason. [B]NB.[/B] If an axle does break on a steep hill you can end up inverted, like [[URL="http://www.ebroadcast.com.au/ecars/News/1999/990324.Bulldog.html"]this[/URL]].
[B]Limited-Slip Diff's.[/B]
[SIZE=-1]4wd.sofcom.com/A/Diff.locks.html
[IMG]http://www.ebroadcast.com.au/ecars/A/PiCs37/Diff.locks.truetrac.jpg[/IMG]
Detroit [I]Truetrac[/I] limited slip differential employs preloaded internal gears. This one is for a Range Rover, available from Ritters of Melbourne, $1150 installed ($au 1999).
[/SIZE] The perfect differential would provide little or no resistance to the differential action when the difference in rotational speed between the output shafts is small, ie. when cornering. It would provide increasing resistance as the difference in speed increases, ie. under wheel spin. Several limited-slip differentials (LSD) approximate this ideal to varying degrees.
The simplest LSDs provide some friction between the side-gears and the diff' centre. This can take the form of spring-loaded plates alternately keyed to the side-gears and to the centre and pressed against each other. The plates are naturally liable to heating and to wear in heavy use and may then become ineffective. The friction also resists the differential action at even low speed differences - and may affect cornering.
Mercedes and Porsche have developed more intelligent (and expensive) systems where the limited-slip plates are pressed together under hydraulic pressure when electronic sensors detect wheel spin.
The viscous-coupling also employs plates but these are not in physical contact with each other. Instead they are in a sealed drum full of viscous fluid (silicone based). They can contra-rotate freely at low speeds, but the resistance increases very rapidly with the speed difference. The precise characteristics of the device can be controlled by the choice of viscous fluid and by drilling holes in the plates. Range-Rovers from the late 1980s-on use a [URL="http://www.ebroadcast.com.au/ecars/LandRover/Mech/VC.html"]viscous-coupling[/URL] in the centre-diff'. (I would be interested to know if a Range-Rover parked on a very steep, loose hill is liable to creep if the rear wheels slip.) Viscous-couplings were developed by Ferguson (of the P99 [URL="http://www.ebroadcast.com.au/ecars/ClassicCars/Racing.html"]F1 car[/URL] and the Jensen FF 4WD sports coupe). They are also used in some front-wheel drive cars.
Almost all open diff's use bevel gears within the centre, but this is not the only possible arrangement. Some early cars (maybe Austin 7 ?) instead used pairs of plain gears to link the two side-gears. You can see that pairs of gears are needed to allow the side-gears to rotate in opposite directions relative to the centre. All of these gears are mounted within the centre. Some modern LSDs use a variation on this theme. Pairs of gears are used but these are mounted in the centre in such a way as to provide a great deal of friction if they rotate at high speed [I]under load[/I]. Unfortunately there is little friction under no load, ie. if one wheel is actually airborne.
Yet another arrangement uses the fact that a fine-pitch worm gear cannot be driven backwards, and that a coarse-pitch worm gear can only be driven backwards with difficulty. These LSDs use pairs of coarse worm gears, mounted in the centre, to drive the side-gears and hence the wheels. Each worm gear contra-rotates with its twin through end gears.
[B]Lockers.[/B]
The Detroit locker is quite different from other differentials. The planet-gears and side-gears are replaced by what appear to be three plates. The middle plate is driven by the crown wheel. A number of cams pass through the middle plate and drive the side plates. These cams will allow the outer, faster-rotating wheel and its plate to overtake the middle plate. This is not a simple ratchet or free-wheel because, and this bit always seems like magic, the device also works correctly in reverse.
Lockers transfer torque to the inner wheel in a corner and the action is not always smooth so they affect steering characteristics and are often advised against for SWB vehicles and for "normal applications". However...... Mark Ritter fitted a [URL="http://www.ebroadcast.com.au/ecars/A/Diff.lockrite.html"]Lock-Right[SIZE=-1]tm[/SIZE][/URL] locker to his 1994 Land-Rover Discovery (full-time 4WD):
[INDENT] [SIZE=-1]On the street there is no change except for a mild clicking noise as the outside wheel unlocks so that it can travel faster in a turn. [And off road] no tire spin or drama, and much more control.
[...]
I have had no "twitchiness" on the road. I think this is due in part to the Disco's full-time 4wd. The twitchiness that you have heard about is generated by the power going to the inside rear wheel when the outside rear unlocks. In a two wheel drive situation each rear wheel would provide 50% power to move the car until you come to a corner. As soon as the outside wheel unlocks, 100% of the power is now going to the inside wheel which would tend to cause understeer. With full-time 4wd the inside rear's share would go from 25% to 33% so the effects are minimal. About the only thing you notice is that it takes a little more pressure on the steering wheel to negotiate a turn.[/SIZE][/INDENT][B]Traction Control.[/B]
Traction control involves no modification to differentials at all. The idea is simply to apply the brake on any spinning wheel. This will slow it down and force torque to go to its opposite number which still has traction. Some trials cars, but no road cars, do have manually operated "fiddle" brakes for individual drive wheels. However, an anti-lock braking system (ABS) already has most of the necessary bits and pieces: a speed sensor for each wheel and the ability to control the braking of each wheel individually. Clearly the normal driving characteristics of the car are not affected. Many luxury cars, including late model [URL="http://www.ebroadcast.com.au/ecars/LandRover/RR2.html"]Range Rovers[/URL] use traction control in conjunction with ABS.
[B]Centre Diff's.[/B]
A few final remarks on centre (transfer-case or gearbox) diff's and full-time 4WD:
The torque-split fore and aft need not be 50:50. If you think about it, the side-gears can be of different sizes and apply different leverages to their respective output shafts. Some 4WD rally cars used 40:60 or 30:70 torque-splits.
A centre-diff' lock on a full-time 4WD is open to abuse - see the manufacturer's handbook. If it is engaged on firm surfaces it can cause transmission wind-up and rapid wear. If it is not engaged on loose surfaces the diff' can overheat and fail; it is small and does everything three or four times faster than the road wheels. It is quite strong enough if used correctly.
- /4WD.html
[B]Reference[/B]:
[1] K. Garrett. Traction control differentials. Automotive Engineer, pp20-26, Feb 1987.
Re: Locker Information Links
Another differential locker article:
From: [url]http://www.4x4web.com.au/skips4x4/articles/difflocks.htm[/url]
[B][B] [B][FONT=Arial][SIZE=6][COLOR=#0000ff]Skip's 4x4[/COLOR][/SIZE][/FONT][FONT=Arial][SIZE=4][COLOR=#0000ff]
[/COLOR][/SIZE][/FONT][/B] [IMG]http://www.4x4web.com.au/skips4x4/images/logo_skips4x4_150.jpg[/IMG][B][FONT=Arial][COLOR=#ff00ff]
[/COLOR][/FONT][/B][FONT=Arial][COLOR=#0000ff] Diff Locks[/COLOR][/FONT][/B][/B]
[FONT=Arial][COLOR=#0000ff][B]By Mark Peacock[/B][/COLOR][/FONT]
[FONT=Arial]The installation of a diff lock on your vehicle somehow adds that mystical quality to your 4WD standing. Some people choose not to let on their ‘secret’ and attempt to cultivate a driving reputation of [I]‘4WD legend’[/I] status. Others boast to all and sundry of their installation and then fail to deliver the magical performance now expected. But really, what is all the hype about diff locks, and is it deserved?[/FONT]
[FONT=Arial]To set the record straight, the diff lock fitted as standard equipment to all permanent 4WD’s does nothing more than make it the same as the "lesser" part-time 4WD’s when in four wheel drive. A permanent 4WD has a centre differential whereas a part-time 4WD does not. The diff lock only locks the centre diff and has nothing to do with the differential on the front and rear axles.[/FONT]
[IMG]http://www.4x4web.com.au/skips4x4/images/mundaring2_m.jpg[/IMG][FONT=Arial]The diff lock most 4WDrivers talk about, and the one refered to in this article, is when its fitted to the front or rear axle of the vehicle. Its here that the mystic begins. A ‘normal’ differential transmits drive to both wheels equally when they receive equal traction, but when one wheel loses traction, the diff actually transmits more drive to that wheel. Hence you can become stuck in 2WD with only one wheel bogged. Similairly, when in 4WD you can be bogged with one front and one rear wheel without traction. So your 4WD is really only a 2WD, with one front and one rear wheel providing all forward momentum.[/FONT]
[FONT=Arial]To overcome this limitation many vehicle manufacturers fit a limited slip differential (LSD) to the rear of most new 4WDs. A LSD is an improvement to the open differential but, as its name implies, it only provides limited drive to the wheel that has traction. To appreciate just how ‘limited’ the slip is, try the following test. With a vehicle fitted with a rear LSD, place an axle stand to lift one of its rear wheels off the ground and then chock both front wheels with a brick. The LSD will not provide enough torque to drive the vehicle over the brick (vehicle obviously in 2WD). If a diff lock was fitted then the vehicle would drive forward easily.[/FONT]
[IMG]http://www.4x4web.com.au/skips4x4/images/detroit_lsd.jpg[/IMG][FONT=Arial]In many offroad circumstances the traction avaliable to the rear wheels is similair and the LSD can control any wheelspin. However as soon as there is a large difference in traction ie. one wheel off the ground, there is no way a LSD will have any beneficial effect. The reason the diff lock is so effective is that it provides equal drive to each wheel, regardless of traction. When a diff lock is fitted to both front and rear, a vehicle has to loose traction to all four wheels before it stops.[/FONT]
[FONT=Arial]Diff locks obviously provide more traction but their effect is more dramatic in certain terrain types. The greatest improvement comes on deeply gouged rocky tracks where there is plenty of traction and the rough ground results in opposite wheels not touching the track. The least improvement comes in smooth slippery tracks where all wheels have roughly the same weight on them but there is simply not enough traction. It is quite common in these circumstances for all four wheels to spin even when diff locks are not fitted. [/FONT]
[FONT=Arial]A diff lock is not some magical device that can create more traction for your vehicle, all it can do is make avaliable the same amount of torque to each wheel. In simplistic terms, a four wheel drive vehicle is only a 2WD whereas a front and rear diff locked vehicle is a true 4WD. In pratical terms, a vehicle with front and rear diff locks will go places that no ordinary 4WD can.[/FONT]
[IMG]http://www.4x4web.com.au/skips4x4/images/detroit_locker.jpg[/IMG][FONT=Arial]So now you can see why to fit a diff lock, but what type? And if fitting to only one diff, is a front or rear fitment more effective. First of all, its better to explain the different types of lockers commonly avaliable. The three most common brands of diff locks comprise of essentially two different types. The [B]Detroit Locker[/B] and the [B]Lock Right[/B] are an automatic locker that are always in operation. They work by leaving the diff locked and automatically unlocking it when required. Without getting technical, they work by transmitting drive equally to both wheels but allow a wheel to turn faster than driven speed, such as required when cornering. The [B]ARB[/B] diff lock is operated by a switch when required and locks the diff completely. It does not allow any difference in wheel speed on the same axle.[/FONT]
[FONT=Arial]The advantage of the automatic lockers is that they allow one wheel to overspeed, thus allowing easier cornering. When fitted to the front diff, this allows steering control to be easily maintained whereas a locked diff tends to go straight ahead. Proponents of locking diffs point out that the diff can be turned off to allow steering control or that it should only be used when traction is so poor it makes no difference to steering. In practice, it is a definite advantage to maintain steering control. However, an automatic locker should not be fitted to the front diff of permanent four wheel drives as it has a noticable effect on steering when on reasonable traction surfaces. When a part-time 4WD is in 2WD there is no effect what so ever on the steering from an auto diff lock. A permanent 4WD’s only option for the front diff is an ARB locker.[/FONT]
[FONT=Arial]The rear axle can have either an automatic locker or ARB locker regardless of being a permanent or part-time 4WD. The overspeed advantages of an automatic locker are minimal on a rear axle fitting as far as steering effect are concerned. The biggest difference is that an automatic locker is ALWAYS working whether in 2 or 4 wheel drive or on dirt or bitumen. In practice, this results in being able to go most places in 2WD whereas 4WD would have been required previously. It is still good practice however to use 4WD as soon as pratical when on dirt as it minimises the impact on the enviroment. [/FONT]
[FONT=Arial]An ARB locker should only be used in the dirt when traction is so poor that one wheel is close to loosing traction, otherwise axle windup may occur if used on good traction surfaces. At this point, it may seem that automatic lockers have it all over the ARB locker but its not quite that cut and dried. Even when fitted to the rear there is an effect on the vehicle by an auto locker as it cams in and out. It is more noticable in short wheel based petrol powered vehicles than in long wheel based diesel vehicles, where the effect is minimal. It occurs mainly when getting off and on the gas in corners and has a lot to do with driving style. It shows up as an audible clicking from the rear and in some circumstances can have a slight understeer effect. Once an auto locker is fitted to the rear this effect will always be present to a varying degree. Most drivers are unaware of this effect, bit if its of any concern you can adapt your driving style to minimise its impact. An ARB locker is only switched on as required so there is no effect during on-road driving.[/FONT]
[FONT=Arial]So now your aware of the differences between the types of lockers avaliable, which is the best place to fit a single diff lock, front or rear? This is actually a loaded question as it depends on the type of terrain and your vehicle type, but in a nutshell I believe the front is the best place. This is especially so for independent front suspension vehicles which easily lift a wheel even on modest terrain. Additionally, most vehicles these days already have a rear LSD so why fit a locker to the rear and leave the front diff open? Its a better option to fit the locker to the front and leave the LSD in place. When the vehicle has open diffs back and front there are still advantages for a front fitment. When in sand or mud the fitting of a locker to the front will have a greater effect. If hill climbs are your main speciality then a rear fitment may be a better choice as there is a significant weight transfer to the rear axle when going uphill. However if the hillclimb requires large rocks, gullies or shelves to be driven over, then a front locker will drive over the obstacle rather than being pushed up it from behind. As you can see, there is no right or wrong answer, just different choices depending on individual factors.[/FONT] [SIZE=1](c) 4WD Encounter 1998[/SIZE]
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Re: Locker Information Links
And yet another article explaining the various types of lockers available as well as differentials and how they work:
From: [url]http://www.offroaders.com/tech/limited-slip-lockers-differentials.htm[/url]
[LEFT][B] [FONT=Verdana][SIZE=3][COLOR=#0000ff]Got Traction?[/COLOR][/SIZE][/FONT][/B][/LEFT]
[LEFT]In the sport of offroading almost inevitably the conversation turns to improving performance. When offroad an important keyword is traction. Better traction generally boils down to four components, your tires. Quality tires designed for offroad make a world of difference in your ability to find traction and have fun. But if a tire is not turning due to a lack of power being sent to that tire, the best tires in the world won't help you. That's where the right differential makes a difference. This article will attempt to explain what role your differential plays in traction and the different types of differentials available on the market and how they will affect your vehicle's traction and handling characteristics. [/LEFT]
[LEFT][B][FONT=Verdana][SIZE=3][COLOR=#0000ff]The Differential[/COLOR][/SIZE][/FONT][/B][/LEFT]
[LEFT]The differential in a vehicle is located in what is sometimes called the "pumpkin", or that center section of the front or rear axle that intersects with the drive shaft. Within that center part of the axle is contained the differential.[B][FONT=Verdana] [/FONT][/B][/LEFT]
[LEFT]In a vehicle, the [B] [FONT=Verdana]differential usually consisting of a set of gears, that allows each of the driving wheels to rotate. The gears convert the rotating motion of the driveshaft or drive train and split power to each of the driving axle shafts of that axle. In 4 wheel drive vehicles there are two differentials, one in the rear axle and one in the front axle.[/FONT][/B][/LEFT]
[LEFT][B][FONT=Verdana]The differential has three jobs. It directs engine power to the wheels. It acts as the final gear reduction in the vehicle, slowing the rotational speed of the transmission (and transfer case of 4 wheel drive vehicles) before it hits the wheels. The differential also transmits the power to the wheels while allowing them to rotate at different speeds, thus the term "differential". [/FONT][/B][/LEFT]
[LEFT][B][FONT=Verdana]The main purpose of the differential is to allow each half of the axle (each tire) to spin at different speeds, while supplying an equal amount of force to each wheel in that axle. The need for [/FONT][/B] [FONT=Verdana][B]the wheels to rotate at different speeds is especially apparent when turning corners. When cornering the inner wheel travels a shorter distance than the outer wheel. With an open differential they both propel the vehicle forward with equal force, so long as both wheels remain in contact with the road and have traction. However if one wheel slips, for instance on ice, more torque is sent to the wheel that spins. If that slipping wheel completely looses traction, all power will be sent to that wheel and you have no forward momentum. [/B][/FONT] [B][FONT=Verdana]When offroad, this is where the common open differential fails to remain effective. When offroad there are many situations where a wheel will spin free. In most stock 4x4 vehicles the common Open Differential can be found in both the front and rear axles. When a wheel in the front AND a wheel in the back are allowed to spin free due to the Open Differentials, that 4x4 is essentially a 2 wheel drive vehicle. One front wheel, and one back wheel. This is where other types of differentials will make drastic improvements to traction.[/FONT][/B][/LEFT]
[LEFT][B][FONT=Verdana][SIZE=3][COLOR=#0000ff]Types of Differentials[/COLOR][/SIZE][/FONT][/B][/LEFT]
[LEFT][FONT=Verdana]Differentials can be generally classified into 4 categories. Open Differentials, Limited Slip Differentials, Locking Differentials and Spools. Spools are really just the elimination of the differential, so really, there are three categories. [/FONT][/LEFT]
[LEFT][FONT=Verdana]Beyond the open differential, the various types of "non-open" differentials will provide varying degrees of limiting of the spin or slip of an open differential. What also varies is the feel of these differentials, which translates into varying degrees of handling characteristics on road and offroad.[/FONT][/LEFT]
[LEFT] [/LEFT]
[LEFT][COLOR=#0000ff][B]Open / Standard Carrier Differential [/B][/COLOR]
The standard differential, or what is referred to as an open carrier, is what comes with most OEM vehicles. The open carrier holds the ring gear in place and within the open carrier is generally a set of gears called spider gears. These spider gears are responsible for allowing [FONT=Verdana]a vehicle to negotiate a turn and allow the outside wheel to travel farther and turn faster than the inside wheel. This type of open design works great for most of vehicles on the road today. However when a vehicle with an open differential meets a lack of traction, it directs power to the wheel with the least amount of resistance. The result is the wheel on the traction-less surface spins free, while the opposite wheel of that axle on the better traction surface provides little or no power. [/FONT][/LEFT]
[LEFT] [/LEFT]
[LEFT][B][FONT=Verdana][COLOR=#0000ff]Limited Slip Differentials, [/COLOR][/FONT][/B][FONT=Verdana][COLOR=#0000ff] [B]Posi-Traction (Posi, Posis)[/B][/COLOR][/FONT][/LEFT]
[LEFT]Limited Slip and positraction (posi) differentials are designed to "limit" the tendency of open differential to send power to a wheel that lacks traction and redirect the power to a degree to the other wheel of the axle. The Limited Slip and Positraction differential will send power to both wheels equally when traveling straight, however when one wheel spins due to a lack of traction, the differential will automatically provide torque to the other wheel with traction. Limited Slip and Positraction (posi) differentials limit the loss of torque to a slipping wheel through various mechanisms such as clutches, gears cones, and other methods dependant on the unit. The limited slip and positraction will not provide 100% lock up of the differential in extreme situations such as when a wheel completely looses traction. Limited Slip and Positraction (posi) differentials are recommended for daily driven vehicles and are used in many applications where traction is sometimes needed as in emergency vehicles. They are also ideal for front axles of 4x4 vehicles that are not equipped with front hubs that can be disengaged. The term [FONT=Verdana]"positraction" ("posi" for short) was used by General Motors years ago for their limited slip differential and has been used to refer to limited slips since. [/FONT][/LEFT]
[LEFT][COLOR=#0000ff][B]CLUTCH-TYPE LIMITED SLIP
GEAR-DRIVEN LIMITED SLIP[/B][/COLOR][/LEFT]
[LEFT] [/LEFT]
[LEFT][FONT=Verdana] [IMG]http://www.offroaders.com/tech/images/diff/tractech-detroit-softlocker.jpg[/IMG][/FONT][B][FONT=Verdana][COLOR=#0000ff]Lockers, Locking Differentials [/COLOR][/FONT][/B][/LEFT]
[LEFT][FONT=Verdana]A locking differential or "Locker" uses a mechanism that allows left and right wheels to "lock" relative to each other and turn at the same speed regardless of which axle has traction and regardless of how little traction a slipping wheel has. In this state, the axle acts more as a "Spool". This means traction can be sent to a wheel that may be planted firmly on the ground while the other wheel of the axle is completely off the ground. In this situation an open differential will spin the free (lifted) wheel sending absolutely no torque to the wheel in the ground. A limited slip in this situation will send some torque to the wheel on the ground but possibly no enough to provide any forward momentum. [/FONT][/LEFT]
[LEFT][FONT=Verdana]Lockers use various mechanisms to provide lock-up and can be divided into two categories, Automatic Lockers and On-Command, or selectable Lockers.[/FONT][/LEFT]
[LEFT][FONT=Verdana] [IMG]http://www.offroaders.com/tech/images/diff/Lock-Right.jpg[/IMG][COLOR=#0000ff][B]Automatic Lockers: [/B] [/COLOR] [/FONT][/LEFT]
[LEFT][FONT=Verdana]Automatic locking differentials are designed to lock both wheels of an axle automatically when torque is applied so that both wheels are providing power. When torque is not being applied such as when the clutch is press down, the differential is allowed to unlock, permitting a variance in wheel speed while negotiating turns. Automatic lockers tend to create odd handling characteristics on the street as they lock and unlock and take some getting used to.[/FONT][/LEFT]
[INDENT] [LEFT][B][FONT=Verdana][SIZE=5][COLOR=#0000ff] [URL="http://www.offroaders.com/tech/Detroit-Locker-automatic-lockers.htm"] [FONT=Verdana][COLOR=#0000ff]Detroit Locker - Automatic Lockers[/COLOR][/FONT][/URL][/COLOR][/SIZE][/FONT][/B][/LEFT]
[LEFT] [B][FONT=Verdana][COLOR=#0000ff][URL="http://www.offroaders.com/tech/lock-right-locker.htm"] [FONT=Arial][COLOR=#0000ff]Lock-Right Locker[/COLOR][/FONT][/URL][/COLOR][/FONT][/B][/LEFT]
[LEFT] [B][URL="http://www.offroaders.com/tech/detroit-ez-locker.htm"][FONT=Arial][COLOR=#0000ff]Detroit EZ Locker[/COLOR][/FONT][/URL][/B][/LEFT]
[LEFT] [B][FONT=Arial][COLOR=#0000ff]Aussie Locker[/COLOR][/FONT][/B][/LEFT]
[LEFT] [B][FONT=Arial][COLOR=#0000ff] [URL="http://www.offroaders.com/tech/Lunchbox-lockers.htm"][FONT=Arial][COLOR=#0000ff] Lunchbox Lockers - What is a Lunchbox Locker?[/COLOR][/FONT][/URL][/COLOR][/FONT][/B][/LEFT]
[LEFT] [B][FONT=Verdana] [URL="http://www.offroaders.com/tech/Lincoln-Lockers-Fozzy-Locker.htm"] [FONT=Arial][COLOR=#0000ff]What are Lincoln Locker & Fozzy Lockers?[/COLOR][/FONT][/URL][/FONT][/B][/LEFT]
[LEFT][B][FONT=Arial][COLOR=#0000ff] [/COLOR][/FONT] [/B][/LEFT]
[/INDENT] [LEFT][FONT=Verdana][COLOR=#0000ff][B]On-Command Lockers ([/B][/COLOR][/FONT][B][FONT=Verdana][SIZE=2][COLOR=#0000ff]Selectable,[/COLOR][/SIZE][/FONT][/B][FONT=Verdana][COLOR=#0000ff][/COLOR][/FONT] [B][FONT=Verdana][SIZE=2][COLOR=#0000ff]Manually Operated[/COLOR][/SIZE][/FONT][/B][FONT=Verdana][COLOR=#0000ff][B]):[/B][/COLOR][/FONT][/LEFT]
[LEFT][FONT=Verdana][B] [IMG]http://www.offroaders.com/tech/images/diff/arb_ani.gif[/IMG][/B][/FONT][B][FONT=Verdana]On-command lockers are the best of both worlds providing the benefits of a locking differential and an open differential. An on-command locker [/FONT] [/B][FONT=Verdana]uses a switch activated electric motor or vacuum diaphragm or a cable / lever to engage the locker. When an on-command locker is not engaged, it acts like a standard open differential with none of the quirky handling characteristics of an automatic locker. When the on-command locker is engaged, the differential locks the axle shafts together where it is now more like a spool with no differential of speed between the wheels of that axle. Some OEM on-command locker designs are available on the market including 1998 and newer Toyota Tacoma and Land Cruiser and the Jeep TJ and JK Rubicons. [/FONT][/LEFT]
[LEFT][B][FONT=Verdana][COLOR=#0000ff]ELECTRIC SELECTABLE LOCKER:[/COLOR][/FONT][/B][/LEFT]
[INDENT] [LEFT][U][COLOR=#0000ff][B][FONT=Verdana] Toyota TRD Locker
[/FONT][FONT=Arial][SIZE=2]Auburn Gear Electronic Locker ECTED[/SIZE][/FONT][/B][/COLOR][/U][/LEFT]
[/INDENT] [LEFT][B][FONT=Verdana][COLOR=#0000ff]PNEUMATIC SELECTABLE LOCKER:[/COLOR][/FONT][/B][/LEFT]
[INDENT] [LEFT][FONT=Verdana][COLOR=#0000ff][B] [URL="http://www.offroaders.com/tech/arb-air-locker.htm"][FONT=Arial][COLOR=#0000ff]ARB Air Locker - About ARB Air Lockers[/COLOR][/FONT][/URL][/B][/COLOR][/FONT][FONT=Arial][COLOR=#0000ff]
[/COLOR][/FONT][FONT=Verdana][COLOR=#0000ff][B][SIZE=2] [URL="http://www.offroaders.com/tech/arb-air-locker.htm"][FONT=Arial][COLOR=#0000ff]How the ARB Air Locker works[/COLOR][/FONT][/URL][/SIZE][/B][/COLOR][/FONT][/LEFT][/INDENT] [LEFT][B][FONT=Verdana][COLOR=#0000ff]MECHANICALLY ACTUATED:[/COLOR][/FONT][/B][/LEFT]
[INDENT] [LEFT][B][URL="http://www.offroaders.com/tech/ox-locker.htm"] [FONT=Arial][COLOR=#0000ff]Ox Locker - About OX Lockers
How the OX Locker Works[/COLOR][/FONT][/URL][/B][/LEFT][/INDENT][LEFT][FONT=Verdana][COLOR=#cc3300] [/COLOR][/FONT][/LEFT]
[LEFT][FONT=Verdana] [IMG]http://www.offroaders.com/tech/images/diff/spool.jpg[/IMG][/FONT][B][FONT=Verdana][COLOR=#0000ff]Spools, Mini Spools[/COLOR][/FONT][/B][/LEFT]
[LEFT][B][FONT=Verdana] Spools are actually the lack of a differential. Spools are a 100% lock-up between both wheels of an axle all the time. Spools are generally used for racing and serious offroad use where little or no street driving is seen by the vehicle and a stronger, lighter rear end is needed. [/FONT][/B][/LEFT]
[FONT=Verdana][COLOR=#cc3300] [IMG]http://www.offroaders.com/tech/images/diff/mini-spool-ford-8-8.jpg[/IMG][/COLOR][/FONT][COLOR=#cc3300] [IMG]http://www.offroaders.com/tech/images/diff/mini-spool.jpg[/IMG][/COLOR]
Re: Locker Information Links
And another article that also shows contact information on the various manufacturers:
From: [URL]http://offroad.automotive.com/74983/0401or-differential-lockers-buyers-guide/index.html[/URL]
[B]Off Road Truck Differential Locker Guide - Lockers Buyer's Guide[/B]
Everything You Need To Lock And Roll
By Christian Lee
Eaton E-LockerAvailable to the public in mid-2002, the Eaton E-Locker provides full axle lock at the push of a button. It's an electronically controlled unit that's compatible with other electronic systems, such as brake-activated traction control and stability control. The E-Locker can be operated in 2-Hi, 4-Hi, or 4-Lo, and requires no lube additives, making it virtually maintenance-free. For more information, contact: Eaton Corporation, [URL="http://www.eaton.com"]www.eaton.com[/URL].
ARB Air LockerHow cool is this? A locking differential that's air activated at the push of a button. The ARB Air Locker is an excellent choice for front diff applications because it can be manually engaged or disengaged. The manual operation is also a benefit if you use your 4x4 as a daily driver since it doesn't affect highway handling characteristics. Check with the company for a listing of its many applications. For more information, contact: ARB USA, Dept. OR, 20 S. Spokane St., Seattle, WA 98134, (206) 264-1669, [URL="http://www.arb.com.au"]www.arb.com.au[/URL].
PowertraxPowertrax offers two locking differentials for many vehicle applications. The No-Slip Traction System combines the qualities of limited-slip and locking devices and eliminates the ratcheting sounds often associated with locking diffs. Also, installation is a cinch because no ring-and-pinion setup is required. The Lock-Right Locker by Powertrax is a fully automatic unit that locks the axles together when the vehicle is traveling straight, but allows for differentiation via internal gears in turns. Both units are available for a number of applications. For more information, contact: Powertrax, Dept. OR, 245 Fischer Ave., Ste. B-4, Costa Mesa, CA 92692, (800) 578-1020, [URL="http://www.powertrax.com"]www.powertrax.com[/URL].
TractechWith the most applications and models to choose from, Tractech is one of the better-known names in the market. It offers its venerable Detroit Locker, Detroit E-Z Locker, and the Detroit Gearless Locker, all of which are speed-sensitive units, in addition to its torque-sensitive (limited-slip) lineup with the Detroit Truetrac and Suretrac. The Detroit Locker is said to be one of the most rugged locking diffs around, and is also the most widely available for axles ranging from 3,000- to 70,000-pound capacities. For more information, contact: Tractech Inc., Dept. OR, 11445 Stephens Dr., P.O. Box 882, Warren, MI 48089, (800) 328-3850, [URL="http://www.tractech.com"]www.tractech.com[/URL].
Zexel TorsenAvailable for GM axle applications, the Zexel Torsen is a full-time torque-sensing, torque-biasing system. Torque and differentiation are continuously managed between the two axles and biased instantaneously according to variable road conditions. There are no clutches or preload to worry about. In fact, the T-1's patented INVEX gearing system is designed to perform for the life of the vehicle. The Torsen T-1 Traction Differential is available in any torque-biasing range from 2.5:1 to 5.0:1 and will fit in most standard GM axlehousings without modification. For more information, contact: Randy's Ring & Pinion, Dept. OR, 11630 Airport Rd., Ste. 300, Everett, WA 98204, (425) 347-1199, (800) 292-1031, [URL="http://www.ringpinion.com"]www.ringpinion.com[/URL].
Auburn GearAuburn Gear offers its Pro Series and High Performance Series limited-slip differentials, both of which are compatible with all ABS and electronic controls, for [URL="http://www.automotive.com/new-cars/01/chrysler/index.html"]Chrysler[/URL], [URL="http://www.automotive.com/new-cars/01/ford/index.html"]Ford[/URL], GM, and [URL="http://www.automotive.com/new-cars/01/toyota/index.html"]Toyota[/URL] applications. The torque transfer capability of the Auburn Gear units is achieved through the use of cone clutches coupled to beveled side gears, which are designed to provide the maximum amount of torque transfer without compromising vehicle performance in situations where torque transfer is not required. For more information, contact: Auburn Gear, Dept. OR, 400 E. Auburn Dr., Auburn, IN 46706-3499, (219) 925-3200, [URL="http://www.auburngear.com"]www.auburngear.com[/URL].
OX LockerIn an unprecedented mix of aerospace and off-road technology, the OX Locker by OX Trax is a locking differential that uses a positive locking cable to mate the axleshafts together and ensure maximum traction. Designed by a high-tech aerospace manufacturer, the OX Locker features a heavy-duty machined diff cover and is available for Dana 30, Dana 35, Dana 44, and Dana 60 applications. New applications are expected during the year. For more information, contact: DriveTrain Direct, Dept. OR, 1477 Davril Cir., Corona, CA 92880, (888) 584-4327, (909) 272-0158, [URL="http://www.drivetraindirect.com"]www.drivetraindirect.com[/URL].
Spicer Trac-LokUsing a clutch plate and disc arrangement designed to create better vehicle control in adverse or changing driving conditions, the Spicer Trac-Lok is a limited-slip differential that uses all the available traction at both wheels. In extreme cases of differences in traction, the wheel with the least amount may spin after the limited-slip has transferred as much torque as possible, which is limited in order to optimize overall vehicle handling. For more information, contact: Dana Corporation, [URL="http://www.dana.com"]www.dana.com[/URL].
Genuine Gear Quik LokDesigned by the makers of the Detroit Locker, the Genuine Gear Quik Lok offers an easy installation, a lifetime warranty, and a low price. Said to be the best standard-duty ratcheting locker offered, the Quik Lok is available for most applications, including the Dana 30, Dana 35, and Dana 44, as well as the Ford 9-inch. For more information, contact: Genuine Gear, (800) 421-1050, [URL="http://www.4wheelparts.com"]www.4wheelparts.com[/URL].
DriveTrain DirectPriding itself on trust, quality, and value, DriveTrain Direct carries everything you'll need to equip your rig with a locking differential. From ring-and-pinion sets, hub conversion kits, axleshafts, and complete axle assemblies and axle assembly packages, DriveTrain Direct offers a bit of everything. For more information, contact: DriveTrain Direct, Dept. OR, 1477 Davril Cir., Corona, CA 92880, (888) 584-4327, (909) 272-0158, [URL="http://www.drivetraindirect.com"]www.drivetraindirect.com[/URL].
SupliersWest Coast DifferentialsIn addition to servicing parts, West Coast Differentials carries a full line of spools, lockers, and posi-tractions made by top-quality manufacturers such as ARB, Auburn Gear, Detroit Locker, Eaton, and Powertrax. The company also offers many years of technical experience, and its tech experts and sales staff can help you decide which locking unit is best suited to your needs. For more information, contact: West Coast Differentials, Dept. OR, 2429 Mercantile Dr., Ste. A, Rancho Cordova, CA 95742, (800) 359-4737, [URL="http://www.differentials.com"]www.differentials.com[/URL].
Drivetrain WarehouseOffering an array of axle components, including a full lineup of lockers, limited-slips, and ring-and-pinion sets, Drivetrain Warehouse is a great source for drivetrain parts. Shown is the Posi Lok Cable Lok designed to replace the factory vacuum diaphragm or heated coil disconnect assemblies that are often prone to failure. The Posi Lok, available for [URL="http://www.automotive.com/new-cars/01/dodge/index.html"]Dodge[/URL], [URL="http://www.automotive.com/new-cars/01/jeep/index.html"]Jeep[/URL], and Chevy applications, ensures instant engagement every time. For more information, contact: Drivetrain Warehouse, (888) 432-7656, [URL="http://www.drivetrainwarehouse.com"]www.drivetrainwarehouse.com[/URL].
U.S. GearServing the drivetrain and transmission industry since 1963, U.S. Gear offers a full line of axle components, including the Torq-Line limited-slip differential. The Torq-Line is available for GM and Ford applications and is designed as a direct replacement for the hard-to-find expensive OEM unit. It's totally rebuildable, cast of nodular steel, and is made in the USA. For more information, contact: United States Gear Corp., Dept. OR, 9420 S. Stony Island Ave., Chicago, IL 60617, (800) 874-3271, [URL="http://www.usgear.com"]www.usgear.com[/URL].
Randy's Ring & PinionKnown as the man with the ring gear halo, Randy Lyman of Randy's Ring & Pinion not only has what you need to outfit your 4x4 with a top-of-the-line locking differential, he can also supply the essential tools needed to install it. Randy also offers a full line of ring-and-pinion sets, axleshafts, spools, rebuild kits, and axle yokes. You might also check out the Web site for excellent technical information. For more information, contact: Randy's Ring & Pinion, Dept. OR, 11630 Airport Rd., Ste. 300, Everett, WA 98204, (425) 347-1199, (800) 292-1031, [URL="http://www.ringpinion.com"]www.ringpinion.com[/URL].
Reider RacingReider Racing Enterprises is a full-line axle component distributor of 28 major product lines, including high-performance ring-and-pinion gearsets and 16 different types of locking and limited-slip differentials. Based in Taylor, Michigan, Reider Racing handles products manufactured by Precision Gear, U.S. Gear, Auburn Gear, PowerTrax, Dana Corp., TracTech, ARB, Timken, CR Services, Mile Marker, Ford, GM, Chrysler, Ford Motorsports, and more. For more information, contact: (800) 356-1330, [URL="http://www.reiderracing.com"]www.reiderracing.com[/URL].
