Shuddering when gently accelerating...

[BALTANAKT]

92 4.0 Automatic. Had a OME lift for 3-4 years. No problems with vibes.

Until this morning.

Seems anytime over 30mph, if I lightly press the accelerator pedal, the Jeep is kind of shuddering. If I accelerate harder it seems to help smooth things out. If I release accelerator it disappears.

I noticed one tire had lost a lot of air, so could have been causing binding in the diff. Filled tire up and things improved a tiny bit, but problem not solved.

Looked at flex plate/bolts - all looks well.

Engine has burly brown dog motor mounts so they're fine. Think I changed the trans mount a few years ago but ill double check. U-joints didn't show any excessive play.

Thinking about pulling the front driveshaft next. Read a lot of posts suggesting to do that. That said, cant imagine how the front shaft would create vibes under acceleration. Seems like you'd find the culprit in the parts getting power.

 

[old_man]

Transmission mounts or centering ball on dual cardan joint.

 

[Unclewolverine]

Tps

 

[BALTANAKT]

Pulled front shaft to no avail.

Next steps:
- Check tranny mount
- New TPS

 

[8Mud]

The last time mine did that it was a bad front axle U-joint. I usually notice they are bad when in 4X and turning a sharp corner, they kind of chunk, chunk, chunk. This time I first noticed on the interstate, it was kind of like an out-of-balance tire, it was worse at a certain speed.
The way I check my front axle U-joints is to first inspect with a good flashlight, if there is rust dust around the bearing cap seal it is shot. Then I jack the tire off the ground and jam a long 3/8 extension through the yoke and gently bounce the extension off the knuckle. I watch the bearing cap seal for any movement with a good flashlight. If it moves at all the bearings haven't got long to live.
If the vibration is from the front axle U-joint it is likely pretty loose.
It may be something else but the front axle U.joints are worth a look. It is part of my annual maintenance routine, it is better to catch them early than to be hundreds of miles from home and have one get really bad, been there done that.

 

[BALTANAKT]

Put in the TPS sensor today. Did not solve problem, but Jeep is running better and downshifting less.

Trans mount looks fine.

Rear driveshaft *might* have a tiny bit of play in front u-joint. Also, I noticed it doesn't spin true at that end. How true are the driveshafts supposed to be?

Tomorrow I will replace both U-joints on the rear driveshaft.

New noises
- Had some sporadic spinning noises today
- Imagine an aluminum disc spinning and then you draw a screw driver across it
- Only happened when pressing the accelerator
- Lasted a few minutes then no more sounds

Like I said before, flex plate looked a-ok. Totally mystified.

 

[RCP Phx]

You may need to pull the engine to verify for cracks in the flex-plate.

 

[BALTANAKT]

Great success.

Put in new rear shaft joints and it seems to have cured the vibrations.

However, I lost a bolt for the cardan-joint up front. Does anyone have one I could buy?

 

[gearwhine]

Great success.

Put in new rear shaft joints and it seems to have cured the vibrations.

However, I lost a bolt for the cardan-joint up front. Does anyone have one I could buy?

Those mounting bolts to the T-case yoke are generic bolts. Just head over to ACE hardware (assuming you have one nearby) with one of the ones you've got to match thread and length. Buy a lock washer with it; I'd likely just replace all 4 though.