Symptoms: Heavy vibration while accelerating, both in 2 and 4wd. Occasional knocking sounds heard. Occasionally will vibrate slightly when stopped too. Smooth when feathering the pedal and in reverse. I do have a flexplate knocking sound but all the bolts are tight and I didn't see any signs of cracking.


I've rebuilt the tcase and swapped another tcase in. The swapped tcase lessened the vibration but didn't fix it.
Changed the trans mount and all ujoints.
Pulled the front driveshaft, no difference
Pulled the rear driveshaft, vibration a bit better but still there.
Engine mounts look good and the engine doesn't jump under torque.


Two shops have looked at it now and say they cant pinpoint it.


Any suggestions on what to do next?

 

I see you have a 3" lift. That could be causing your vibes. Try dropping the t-case down an inch and see if that helps.

 

Tcase is dropped one inch

 

how is the pinion angle? did you shim it when the lift was installed? it could be axle wrap. As you accelerate the pinion has a tendency to rotate possibly causing a vibration.

 

Right, and I actually haven't measured the pinion angle. But I did pull the rear driveshaft and drove with only the front and the problem was still there so that made me think it wasn't a pinion angle issue

 

you have a low pinion D30 in the front so the pinion angle will come into play up front as well. I would check both out adjust and see what happens. You might need adjustable upper control arms in the front to fix that. out back you will need angle shims under the leaf pack.

 

Gotcha, I will check those out. Thanks for the advice!

 

no problem here to help

 

Update: Pinion angles look ok. Changed the transmission fluid and the passenger motor mount, helped with the vibration but didn't fix it. My rear axle is half an inch off center, could that be a cause?

 

No.

Pull your front DS and drive it.


BTW, it's generally the driver's engine mount that goes bad........for the $12, change it.

 

I've tried pulling the ds before and it didn't change anything but I'll pull it again and see if all the repairs I've done have changed anything. Drivers side mount looks ok but I'll change that too

 

What about a cracked flexplate? Can that cause this kind of vibration? (possibly a dumb question). I do have what sounds like loose torque converter bolts. I checked those a while ago and they were tight, didn't see any cracks but I know they can be really hard to see