Vibration

[Cr33p3r]

Noticed since I installed the lift kit that there is a vibration and you can feel it thru the floor and pedals. It only happens at 30mph and if I slow down to 28mph it fades away or the same if I speed up to 31mph. Not sure what would cause it at only this speed, any ideas? I've checked everything and it is all tight with no rub marks on anything.

[MultiScuf]

How much lift?

[Robert B]

driveshafts / u joints would be first thing to look at

[dieseldoc]

Tire are the first thing to look at. Get them balanced again.
Then check the allignment. Just a touch out will cause drive line vibrations.
Hell I was fighting death wobble for a year or so....
Come to figure out it was the sway bar was limiting the front end to the point that the caster angles were wrong thus creating death wobble.

So your little bit of lift could cause drive line vibrations....

[Bob]

To see if it is the driveline: Note the RPMs when it occurs. Then change to a higher or lower gear and see what RPM it occurs at. If it's about the same RPM even though the vehicle speed is different, then likely the driveline is the issue.

It's not unusual to have a driveline vibration after a lift because the u-joint angles on each end may be too different.

[The StRanger]

if it wasn't vib before the lift and now after The 1st thing Id look at is U joint angles..

[94ToyBear]

Agree, u joints first then alignment

[dieseldoc]

If the caster angle is off/ pinikn angle off, this causes vibration in the ujoints.
Thus check the alignment.

[Spieg]

Alignment should be checked after any repair/modification to suspension or steering. Every reputable lift kit maker will state this in their documentation. Assuming this was done as part of the lift install, I would look at u-joints/drive shafts next.

[Jim]

Does the vibration seem in sync with tire rotation (wheel/tire related) or 4x tire rotation (driveshaft related)?

30mph does not give a too fast tire rotation speed.

[dieseldoc]

30 mhp is a low tire speed for sure.
But posible....

Drive line if the alignment is off will do this right about that rpm range.....

I bet one of the pi ion angles is just slightly off

[94ToyBear]

I wonder if your experiencing a slight death wobble?
Did you replace Trac bars?

I still call pinion first.

[dieseldoc]

I think pinion as well.
The front one I bet.

[Cr33p3r]

It is the Rubicon Express 3" front and the 2" rear lift. Alignment is good, the links and track bar are factory. After thinking about this it didn't start doing this until I bounced the fuel tank skid plate off a good size rock on Yankee hill which also shoved the slider on the passenger side up into the pinch weld, and that is when the passenger front door started leaking too. Checked everything out and there is no misalignment with the door or jam and the nothing underneath is bent except skid plate.
As for shifting it is a automatic and the vibration starts at 30 mph which is also when the tranny is just about ready to shift in to 3rd gear. Had a vibration like this right after the lift install but discovered the transfer case skid plate needed a 1/4" spacer to lower it away from the exhaust after installing the 3" exhaust extension. Tomorrow I am going to dig deeper into it since it is supposed to be in the 40s.

[dieseldoc]

Degree finder is needed at this point.
If the pinions are not the same as the tcase out puts this will couse a vibration in the drive shaft.
30 mph and thats the only time it does it?
Just at the 3rd to 4th or does it do it at the 4th to 5th?

[Cr33p3r]

30mph is the only time it does it and its from 2nd to 3rd

[dieseldoc]

Hmm....odd.

[94ToyBear]

What i imagine is, at 30 mph, and just before shifting, the pinion is loading (changing angle) up in the front
Your is a slight death wabble.

[94ToyBear]

If you dont figure it out by next we you can come by my place and i can help you out.

[dieseldoc]

There are so many little things that contribute to vibrations up front......
Mine was the dam sway bar keeping the front pulled down thus death wobble here and there....
Didnt matter how hard we tried to get the allognment right.....
No more front sway dar as we ripped a end link a spring creek....
I noticed the next day that the woddle had gone....
Had me a spot on the wat to work that I could make it do it every day.
So ditched that thing...