CPC1

After a transmission fluid change that were made last month the Jeep developped some sort of high frequency vibration that was felt in the steering wheel, the pedals, even the driver seat. It Didn't occur to me that it could be driveline related and thought it was some kind of steering component. here's the list of everything that has been replaced/ upgraded/ checked:
- upper and lower ball joints/ drag link/ tie-rod ends
- HD steering stabilizer
- No play in the trackbar (no ovaled holes)
- Front control arms bushings
- Front brake new rotors/ pads/ caliper is not sticking
- Tires balanced and rotated
- Allignement ( toe in 1/16" caster 4.1)
- steering box and steering shaft are tight
- Axle housing is not bent / When rotated on jack stand front tires doesnt wobble ( so the axleshaft is not bent)

STILL THE SAME VIBRATION!!

There's no vibration at idle when the JK is stopped it only starts as soon as the wheel start spinning so its probably not the engine mounts. Its not RPM nor speed related (same at any speed). I have a 2.5 BB on a 4dr which shouldnt be affecting my stock driveshaft angles.
So I narrowed it all down to transmission mounts being loose or bad.
Am I thinking in the right direction?
how can I check the mounts? and are they easy to replace?

Sorry for the long post.
but this is driving me nuts so any help would be welcomed.

wayoflife

that you have a 2.5 BB on a 4-door means nothing. it is entirely possible that you have a drive shaft that is out of balance and that could easily happen if you knocked off a weight while wheeling or bent it. if you have a torn slip shaft boot, it could be that it's seizing up and has done damage to your cv joint. i would not rules out a drive shaft issue so quickly as a vibration like this is almost always related to it.

rinkishJK

Is this a manual transmission?? If so maybe they removed the mount bolts to jack the trans up to get to the drain. Then when they let it back down they put pressure on the mount while tightening the nuts.
I made this mistake before when I noticed the rubber "feet" on the mount weren't sitting straight.
Went right back and loosened mount nuts, moved trans around till it settled, retightned and buzz gone.

CPC1

Thanks for clarifying that. I will definetly check the shaft boot for any damage.
If the boot turns out to be fine, can the cv joints be shot anyway? The JK hav almost 100k on it.
How to diagnose a out of balance driveshaft and how to rebalance it?
Thanks

CPC1

Its an auto transmission. but what difference does it make? they could have done the same mistake on an auto transmission while draining it. This might as well be the cause of my vibration. Where are those rubber "feet" located so I check it out?

wayoflife

they most certainly can be bad as that is a lot of miles and anything with moving parts will go bad.

regarding balance, just do a visual inspection of your shafts first to make sure there are no dents or what appears to be something missing that was clearly welded on. if one or both are off, i would look into getting a new shaft.

rinkishJK

Here are pics of the mounts.. I just took these and apparently mine are cracked. U can see also the mount inside the crossmember are slotted for adjustment..

CPC1

Thanks that's very helpful

Hook-Em

Another way to test the front drive shaft is to remove it from the equation and see if anything changes. Take the drive shaft off of the Jeep and drive it. If the vibration persists, you've at least eliminated the drive shaft from the bucket list of potential culprits.

Alternatively you could do this with the rear drive shaft as well, although I'll caution you to keep speeds down and steering to a minimum because you'll have to be driving in 4HI.

mvnolan

I have to agree with the drive shaft angle on this one. I just replaced my rear DS and have significantly less vibration now. The stock DS is a POS. The drive shafts are pretty easy to drop, and that should tell the tale. Good luck man.