BrainDead

Hey everyone, as much as I hate to post a possible redundant thread I have yet to find anything on this forum or any other jeep forum that explains my problem.

Long story short I didn't have any sort of noises until I put new leaf springs and shocks in my 98 Cherokee.

Once I had replaced said parts I began to notice vibrations upon acceleration, vibrations tapered off as I exceeded 40mph, at which point I would feather off the throttle and "coast" and notice almost what sounds like excessive backlash from the ring and pinion. If I tap on and off the throttle I get a clunk. If I hold the pedal in just the right spot at about 60 I almost can get a picture in my head of the ring and pinion rattling together....however, Rather than jump the gun I did research and replaced all my u joints( put antiseize on the DS splines) as well as replaced the transmission mount, I also put new diff fluids f/r.figuring that my new springs had brought the driveline angles back in check and exposed a bad u joint. Much to my disappointment after replacing all those parts I still have the problem.
I have no pinion play. However I notice backlash when I turn the DS with the rear end jacked up. How much backlash is too much? And can excessive backlash be causing my issues?

Again, I apologize if this has been covered numerous times, I spent the last few days trying to find someone with a similar description of my problem. Thanks for any help.

XJwonders

The pinion angle may have changed. Did u change the leaf springs to a lifted set?

BrainDead

I replaced my worn out leaf springs with the dorman replacements p/n 929-301.

Now that you mention it I did fail to check my pinion angle when I installed my new leaf packs. Just went out and looked and the pinion seems to be sitting much lower relative to the t-case.

Gatchmo5710

Did u apply final torque with weight on wheels. Sometimes weird stuff happens when bolts are torqued on stands. Then it's constantly bidding on the ground.

IJM

Do you also notice the vibration around 75-80 mph while on the gas? I ask because I have a very similar problem with my '98 (I also replaced the sagging rear leafs recently with the same Doormans), and it does the vibration both around 35-40 and 75-80 or so. The driveshaft U-joints seem tight, though I have no idea how old they are.

I was sure to do final torquing of the leafs and shackles with weight on the rear.

BrainDead

I went out and retorqued everything earlier this morning, still have the issue. I'm not entirely sure I can modify the pinion angle, given that the plate that is welded to the axle "seats" the axle to the angle once the U bolts are torqued down.

Is shimming recommended if necessary? I've only had the leafs in for about 3 weeks, maybe they will "settle" enough to bring the angle back? Or doubtful?

BrainDead

I don't notice anything while on the gas at 75-80 mph. However, if I coast at that speed I hear almost what sounds like ring and pinion chatter until I get back on the gas.

My jeep has 167,xxx on the ticker...

Rogue4x4

Degree shims. Measure the SY ujoint angles and the pinion yoke angles. Should be within 1-3* of each other. Assuming you don't have a SYE installed. If greater than 3* difference, your driveshaft is out of phase.

BrainDead

Just went out and checked the angle at the t case as well as the pinion. I'm right at a 3 degree difference, I don't thing that's my problem. I do plan on doing the SYE kit in the near future...

IJM

Is that even likely at stock height? I always figured that's the kind of thing you have to watch our for when you do a 4"+ lift.

BrainDead

I agree, based on my research I only see degree shims mentioned when regarding lift kits. I'm thinking I have to tear into the rear ended and do axle bearings and a pinion bearing and see if that fixes it.

Is it worth removing the front shaft to single out the rear?

IJM

If it only does it under acceleration, than that would eliminate the front, assuming you're in 2WD.

BrainDead

The vibrations happen on acceleration, yes. But the vibration turns to chatter right when my foot is taken off the gas for a brief moment. until it almost seems like the ring and pinion seat each other and it quiets down entirely.

Rogue4x4

You stated you're right at 3*...probably on the ragged edge. Lift kit or not, you changed a lot of stuff, so you need to try to get it as close to even as possible. Degree shims are a cheap and easy thing to do. 2* shims may fix it.

IJM

Hmmm... I should probably check mine.


How did you measure the angle?