I've researched a bunch of causes of vibrations at highway speeds but I'm not sure if they line up with the symptom.

Im not sure how long the issue has been there since I mostly do town driving. I drove to big bear and at 70mph and 2200rpm, I get a shudder through the car like I'm driving over reflectors. If I accelerate or let off the gas it goes away. so it's strictly at that rpm and speed.

I always had some slight vibration at 55 but it was intermittent.

This one is constant.

Just wondering if this is typical vibration and to pursue the usual fixes. Tires and wheels. Steering linkages and ball joints. Brakes. Etc.

 

If it happens only at one speed it could be the ujoints. But I'd start with balancing the tires.

 

Based on this I would say it's somewhere in the driveline. Maybe start with looking at the u-joints? I'm sure someone else can chime in on this.

I think if it had to do with tire balancing it would be all the time, regardless of whether you're on the throttle or coasting.

 

I bought a junkyard drive shaft to use in the rear end for now since I got an SYE. My front one is rebuilt. I may yank the rear one and move the front one to the back and see if it helps.

If so then I'll rebuild the junker.

 

Disconnect the rear driveshaft and twist the ujoint with your hand. You should be able to feel if it's binding or just not smooth. Cheap and easy to replace. If it was a junkyard driveshaft chances are high the ujoint is toast.

 

Don't know if it's true or not, but have seen mention that the joints kind of take a "set" from working at a specific angle. IMO, if you swap yours for a test, make it a short one.
Or just man up, rebuild rear (good preventive maintenance) and if it doesn't cure it, don't drive 70 until you figure it out. Could even be slip joint, did you grease it?

 

This rear drive shaft I have is off the front of another Cherokee.

I want to just rebuild it but do you think rebuilding the DC is worth it? And where can you find the rebuild kits? I only found one online but it wasn't for my Jeep. Not sure how universal they are.

 

Just an update, I haven't swapped driveshafts yet but the vibration is now present at 60+mph. I'm wondering if it could be the wheel hub bearing. It seems to be coming from the front left.

 

Got three joints and center ball from O'rielys.

Just have to start checking everything.

 

http://www.oreillyauto.com/site/c/de.../617/03943.oap

Is that the center ball?

 

Looks like it, number kinda rings a bell. It comes with a little cardboard sleeve to hold rollers in. Pull that and grease it more before assembly. That whole thing is a Chinese puzzle, especially disassembly. Mark pieces for alignment.

I also used their greasable joints.

Also check that the pinion isn't sloppy, and slip joint is good.

 

So it turns out the insane vibration was caused by the passenger-side tie rod end joint being completely shot. Replaced it, vibration gone.

Clacking noise arose a couple days ago. Just pulled the front driveshaft that had been rebuilt and the ball was riding against nothing and one of the ridges that held the u-joint end on had broken off. The DC joint was binding up terribly when I was trying to move it around. Needless to say, the guy who rebuilt it fudged up somehow or I didn't keep up with greasing it. I need a new driveshaft though. =P