I could use some insight from the forum friends.


I have a 2001 Jeep Cherokee Sport, 163,000 miles, 4.5" Rubicon lift, with 33" BFG's. Tom Wood custom rear driveshaft, and NP231 transfer case.


Recently I've been getting some vibration felt through the gas pedal, and a whirring sound as I decelerate to a stop. I feel they're connected in some way. Here is what I've done recently, so these might be eliminated from discussion.


New axle bearings on rear axle
All new U-joints on rear axle.
New centering ball on rear cardan joint.
Complete transfer case rebuild with all new parts.
New front wheel hub assemblies on front axle.


All these replacements have been made in the last couple months, and I cannot pinpoint where to attack next. I removed the front driveshaft, which eliminated the whirring sound upon deceleration before stopping, but the vibration still exists through the gas pedal. I have no play in my pinion bearings when the shaft is attached, nor do the U-joints appear bad. I'm not well versed enough with the mechanics of the front axle, but I feel something is off in that general area. Four wheel drive did appear rougher than normal (when front shaft was attached) when it was engaged. I removed the front diff cover and drained the fluid, which did have a bit of a metallic appearance unfortunately. Any thoughts? I'm open to anything, since this is really kind of driving me nuts, and I'm sick of throwing money at the problem only for nothing to get corrected. On the bright side, I suppose all the above got replaced new in the meantime.

 

The vibration sounds typical of u-joints but you already addressed that one. The whirring noise could be either a wheel or carrier bearing going out. The vibration in the gas could be some kind of misfire, but I would think you could feel that at idle also. You might be able to go with a 75w140 lucas gear oil and see if it gets any quieter, and at least narrow down if it is internal to the axle or not. Just my thoughts, but hope it helps

 

I just went through similar issue recently. Only felt it under load when pressing on gas. It was the ujoint on rear drive shaft causing mine. I could not feel any problem in joint until I removed the DS. Then it was obviously bad when moving the yoke by hand.

 

Just to confirm, did this issue start randomly after your lift? Meaning, it didn't start when you lifted it? You should post a picture of your front pinion angle so we can at least eliminate that. My front end vibes were due to a poor front driveshaft pinion angle after my lift.

 

When you replaced the front wheel hub assemblies, did you check the condition of your axle shaft ujoints?