Drive line vibrations (only when under load)

I have my Jeep that over the last few weeks i have been experiencing additional drive line vibrations when the throttle is pressed in. the vibrations are the same regardless of the amount the throttle is opened or what gear or even speed. The second I let off the throttle the vibrations go away and have just the normal vibrations from my big tires.

I thought I might be from the front drive shaft the front axle had no play but the connection to the transfer case appeared sloppy (guess it should be since in 2-wheel drive the front axle is not "connected"). but after pulling the front drive shaft the vibrations are still present.

Any idea on what might cause this vibration when under load and not when coasting? and when I mean load it could be 5% throttle when on a decline or 100% throttle and down shifting into 3rd or even 2nd.

Thanks for any help any one can provide.

Check the u-joints and dc joint in the rear driveshaft.

sounds like axle wrap. rear pinion is up too high, shim it back down a few degrees or more depending on your measurements. Also, check/replace Rear U joints.

A new vibe that happens only on acceleration, or only on deceleration, is almost always a worn u-joint.

I will check out the U-joints. I am not sure if this has to do with it also but it also seams like the jeep now when I put it into park move/roles more before the parking pin actually engages in the transmission. likely I am just noticing that more. and also when I let off the gas suddenly or from coasting get on the gas suddenly there is a bit of a clunk.

I put the transmission neutral while driving down the road and reved the motor and it reved smooth...

I will look at the U joints. Might be doing a U-joint swap on the rear drive shaft today.

s far as the axle wrap, I am on HD OEM springs w/ OME shocks. I am only about 2" lifted and have a rear crossmember drop of 1". the suspension setup has not changed for 3 years and I am now just getting it, so don't think its axle wrap. Thank you though.

Also its the rear drive shaft, so no DC joint. just the two U-joints.

While you are under it check and tighten the U bolts on the axle and springs.Mine came loose and they was on my jeep for years. Plus like everybody else said, Check the U-Joints.

another vote for ujoints. every time i've seen a load only vibe it was a bad ujoint.

axlewrap would only cause a problem on rapid acceleration, once you were maintaining a constant speed the vibes would go away.

also the clunk when you let off the gas rapidly is almost certainly a bad trans mount.

The trans mount is bad... have had the replacement for 4 years now... just have not gotten it on... looks like I have some work to do on the Jeep..... Also when I attempted to replace it last time it was a wrong joint and some cross threading was done on one of the bolts. Just work and its really dirty under my jeep. ...

I will check all the axle and other nuts and bolts and grease all the fittings also. That also needs to be done.

Thanks for all the feed back

Thanks for the recomendations. Should have looked at this sooner.





I was not to far away from completely blowing out the U-joint and being left on the side of the road.

Only 1 was really bad but replaced both. Kept the old one as a spare. got the Precision (Federal Mogul) HD w/ fitting. fitting appears not to be a zerk fitting so will need to get the needle attachment for my grease gun.

I may attach the transmission mount tomorrow or Monday. time to take the jeep for a drive to see how it feels.

THANKS for the help!!!!

thanks for reporting back! it helps others who search for similar problems.

glad it was the cheap fix :thumbup:

I have a similar vibration in 5 speed XJ I just got.My other two XJ's don't have the vibration .It's not real nasty but it comes on about 2000 rpm in each gear when accelerating. Very smooth when maintaining speed or decelerating.No unusual noises when the vibration occurs
I replaced both rear U Joints (worn out) and it's still exactly the same.
The tailpipe is very close to the rear leaf spring but doesn't touch

not sure on yours. I wanted to see where it might be coming from so I pulled the front drive shaft, still had it. that removed the front axle and front drive line. when driving along at speed, I put it into neutral and the reved the motor to see if there was any problem with the motor or the connection through the TQ converter. it went up and down in revs nice a smooth.

so I had determined it was between the transmission and the rear wheels. since my case it was only when TQ was being applied and under any load from maintaining to full hard acceleration I did not know what part would do that. I recently had the transmission rebuilt (now it has been about 5 years ago though...) so assumed it could have been the transfer case or the rear axle.

I thought I had rebuilt the rear drive shaft with new U joints 3 years ago so did not think that was it, but recalling from memory I think I rebuilt the front with new joints, not the drive shaft.

I have an extra 29 spline C8.25 I can drop in if that was the case, and I even have an extra rear drive shaft. my fear was that it would be the transfer case. something I don't have an extra of or can easily get and costs a bit more than $50 in u-joint

being a manual you have some other bits that it may be. perhaps clutch issues or through out bearing? What is very close in terms of the exhaust? motor mounts perhaps? given the loading of the motor the engine, transmission, and TC will all shift and move more than you may think. Due to my bad transmission mount I am only 1/4" away from the exhaust and I believe that I get some contact between the two under certain conditions.

Magus2727 said:

being a manual you have some other bits that it may be. perhaps clutch issues or through out bearing? What is very close in terms of the exhaust? motor mounts perhaps? given the loading of the motor the engine, transmission, and TC will all shift and move more than you may think. Due to my bad transmission mount I am only 1/4" away from the exhaust and I believe that I get some contact between the two under certain conditions.

Click to expand...

Generally a engine or clutch balance issue will show up in neutral when the engine is reved up,clutch in or out. But this one is smooth except when accelerating. It's only raised about 2 inches so driveline angle should be ok. Yes,very close on the pipe to rear axle,the pipe does scrape on the rear spring when doing mild off road or making a fast right hand turn.So maybe the pipe does touch when accelerating but doesn't make the usual pipe to chassis rattle sound.
It hasolder worn tires,is it possible for a tire to cause a vibration when accelerating then be smooth otherwise?
And I would say the front outer U joints are due for replacement....
maybe I need to fix a few more things

check the condition of the trans mount, my 94/ax15/4.0 would flex with torque when I got on it and let the exhaust pipe hit the transmission crossmember. replaced the mount and it went away.