Doobby

From what I've seen, there are countless threads related to vibration. Hope that this isnt' repetitive for some folks. Anyway....

This is not my first Cherokee. My other two ran well ove 200K miles, but this is the fist time that I've chased such a problem. I bought this gal at a car show without a test drive. She's bone stock.

When I got her on the highway, there was a tremendous vibration that felt like something out of balance. At highway speed you had to raise your voice to talk.

After I got her home, the first thing that I was told to try was the front prop shaft. I pulled it off and the problem went away, for the most part (noises/vibes noticed in the rear, but not as bad. I'm sure I'll ask questions about this in another thread later). Sure enough the double cardon joint was bad. I rebuilt the prop shaft. The shaft wasn't visible dinged or bent. It looks perfect. All weights still appear to be there. There's no evidence of anything missing.

Confident that I solved the problem, I reinstalled the shaft, and took her for a test drive. I was disappointed to find that the heavy out of balance feeling and noise was gone, but another vibration was still there. Still in the front end. I was noticeable at slower speeds, but really shows itself at about 60mph. Took the prop shaft back off and the problem went away. My question is this: with a good, rebuilt drive shaft, what could still be vibrating in the front end?

The vibration correlates to highway speed, not engine RPM's.

My speculation is that it's something in the front differential. A pinion or carrier bearing? The yoke? My next question is this: If the running gear is still in good shape, can the front diff rebuild be performed my a shade tree guy like myself? Will the shim pack remain the same with the same gear set? It it possible to just replace the bearings without all of the additional setup (minus the preload of the bearings that is necessary)?

Am I even barking up the right tree, or am I way off base?

Any thoughts would be appreciated.

Doobby

I was able to crawl underneath and check the yoke. The yoke doesn't have any (detectable) play side to side, but it does have considerable play in and out. It's not play between the yoke and the pinion. It seems like the yoke and the attached pinion shaft move in and out.

From what I've researched about the rebuild/set-up of the differential, the bearings are pre-loaded then checked by an inch-pound torque wrench. With this type of pre-load, my guess is that if the differential was correct, the preload alone would not allow the pinion shaft to move in and out.

Is this helpful information? Am I on the right track?

kstopp

Might I ask what parts you used to rebuild the front double cardan shaft? Did you use Spicer parts? Is there any play in the driveshaft slip yoke?

How are the axle u-joints? These joints are spinning whenever the wheels are turning so it's probably not them though.

BTW fill out your profile more completely.

NM-XJ

I had a similar issue last year. Thought it was "death wiggle", if you will, and rebuilt my steering. Also ended up doing track bar, shocks, balance and alignment to try and solve it. Check out my threads for more details.

In the end it was just a massive nail in my front right tire. No more nail, no more vibrations. Why it wasn't caught during balancing is beyond me.

It could be a number of things, and might not be something in your tire like mine. But check your tires before dropping $$$ on new parts!

JeepMN

I've had the same problems as you. I had my driveshaft rebuilt and still couldn't stop the vibes. Mine ended up being the yoke.The ears on the edges wore down and allowed the u joint to move just the slightest bit when moving... Which caused a massive vibration. Easy fix if you have the same problem

Doobby

I'll fill out the profile more completely asap.

Slip joint seems to be ok. No play side to side. Obviously it moves in an out, but it moves smoothly. There is a collar that seems loose (maybe. Not sure what it's supposed to be like). Couldn't vouch for the parts used. I got them from a local spring company (Wheeling Spring) that does this type of work.

Tires checked. The first order of business was to have the tires broken down and the white letters put on the outside. Rebalanced and rotated. This eliminiated the shimmy in the steering wheel.

The yoke seems tight. Checked the fit with the prop shaft installed and all looks good. It would be cheap enough to replace the yoke, but replacement would affect the preload on the pinion shaft bearings (I think). Thoughts on this would be appreciated.

I have had the "death wobble" at highway speed. I'm trying to chase this problem down as well.

I would have to agree that it's not the axle u joints because with the prop shaft out they're still rotating. At highway speed with the shaft out it's smooth.

I'm leaning toward the prop shaft, yoke, or pinion bearings. Despite rebuilding the prop shaft, there could still be unseen issues.

Still open for all the advice that anyone can give.

JeepMN

The yoke will seem fine as long as the shaft is installed. You must take off the u straps and check to see if your u-joint can move at all with no tension on it. I accidentally found my problem while installing my driveshaft and noticed my u joint wasn't seating properly. And no, every Dana 30 uses shims instead of a crush sleeve so taking your yoke off will have no effect on your preload or backlash.