drive line noise

[SubAlpine]

I am hearing some drive line noise.
98 4runner 3.4l auto

Whirring sound, from the front driver side
under acceleration
not in park or neutral while at a stop

It does not occur unless under load, moving and accelerating.

checked fluids, and all are good.

As it does not occur when the motor is revved in park, I think it is not engine related?
CV's re greased in June.

[The StRanger]

Intermediate bearing ??

[Robert B]

does the noise change related to speed??
and correct me if im wrong but the diff is on the driver side yes ??? and does the axle spin all the time (fully connected to the wheel) if these 2 things are both true then i would say a wheel bearing is a high possibility or a diff issue

[SubAlpine]

The diff is pretty well centered, but I suppose a bit to the drivers side. I checked the fluid in the diff, was good. It does not have manual hubs, equipped with automatic disconnecting differential. Yes the sound modulates a bit with speed.

[Patrolman]

Robert - you are correct, this is a driver side diff with ADD. There is a disconnecting shaft in the front, so the hubs are always locked.

Chris - You mentioned under load? So if you are coasting downhill it doesn't make the sound? If in doubt, you might try coasting a bit with the engine off. That would certainly eliminate any engine noise. I am going to lean toward wheel bearing based on what I have heard so far, but it could also be the brakes. There is typically a piece on the brake pads that are supposed to make noise when the pad is getting low so that you don't score the rotor. That typically isn't associated with driving under load or coasting though. It is usually while braking.

[Jim]

Is the vibration or sound of a similar frequency of the wheel rotation or is it about 4x the frequency of wheel rotation?

If 1:1 with wheel rotation - axle bearings.

If ~4:1 of wheel rotation - driveshaft/pinion bearing related

[94ToyBear]

I vote pinon/diff bearing 1st...unfortunately
Wheel bearing 2nd.

What area are you in ?

[Rick]

94ToyBear previously posted:

[SubAlpine]

huh, not sure about the ratio. I will have to listen to that tomorrow.

[SubAlpine]

dumb question. The sound seems really local to the front drivers side. Front diff have pinions?

[Rick]

found this....has some info you may like... http://home.4x4wire.com/erik/diffs/

[SubAlpine]

been picking through that page. Lots of info there. Is there a way to isolate the front diff to diagnose? If I remove the front drive shaft, the diff will still spin because I do not have manual hubs? Just want to have a better idea of what I am going to be getting into before I ask the boss for money.

[Jim]

Do you have a camera / GoPro that you can mount at various locations under the chassis? If yes, it might help locate where the sound is the loudest.

[Rick]

http://www.tetongravity.com/forums/s...blem-%28NSR%29

[Rick]

http://www.toyota-4runner.org/4th-ge...e-driving.html

[SubAlpine]

Great, I will do some test drive situations tomorrow. Am I to assume that if there is no difference in turning left or right that it may be more likely to be diff related?

[Rick]

that would be my guess

[94ToyBear]

I have a 4post lift at work, I can help you out if you like. It shouldn't take long. Im off of 26th and federal.
Looks like you in lakewood so not to far.
Pm me if your interested and ill shoot you my number

SubAlpine previously posted:

[Chris]

Lots of ideas here but I didn't see anyone mention the tensioner pulley which is what I would start with. Pretty common with Yota's.

[SubAlpine]

On further observation,
noise ONLY occurs while on the throttle. No noise when slowing down, or coasting.
Noise is louder at the bottom end of each gear, and gets quieter as the engine revs, then gets louder after the transmission shifts.
No difference when turning in either direction.
Slight noise while in gear, on breaks at a stop, almost inaudible.

So I guess what confuses me is if it is a wheel bearing or pinion gear, the noise should be present whenever the vehicle is moving, because the affected bearing would be moving regardless of throttle position?
On the other hand, if it is a pulley, the noise should be present whenever the engine is turning, ie. weather the engine is in gear or not, it should make the noise, not dependent on the transmission?