AND WHAT WAS THAT!

[RedLightRubi]

hey, the jeeps a little broke and just asking for any suggestions.... Many of you have years more experience then me with Jeeps, and I am at a loss.
Here are the symptoms

1) Grinding/Thumping noise when under load which goes away when I let off the gas.
2) the noise gets faster/slower with accel/decel
3) grinding is worse when decel in 4wd
4) before parking it noticed a slight squeak at slow speed
5) cant tell where the noise is coming from since the uni-body transfers sound into the cabin
Now, i checked the T/C and its topped off, as is the rear dif.
Rear ds is solid, doesn't rotate or shift when in park
Front ds rotates when in park about a quarter inch side to side
No visual leaks from front/rear difs, T/C, or Tranny

ANY suggestions would be greatly appreciated
Thanks,

Nick

[Keith C]

Some of that is a bit confusing, but I can point you to a couple spots to check:
1. Front and rear driveshaft u-joints. You might need to actually unbolt on end (axle is easiest) to feel how bad the joints are.
2. Front disc brakes? Jack the tire and spin the wheel listening for a stuck caliper and friction or something.

I have had those types of noises from both situations and the darn noises can be mis-leading. Good luck.

[Jon W]

You may want to check your diffs... And your wheel bearings (front & rear). I'm not sure you should have much/any play in the front driveshaft the way you describe it...

The only real play in the front shaft should be the backlash of the ring/pinion, which you shouldn't be able to feel.

If you have it in 4wd parked, does the front shaft still have play?

If you twist the front shaft in 2WD can you hear a clunking in your front diff? If so you may want to pop the cover and look at the gears.

A few things I've done to isolate noises:
1) If you can hear the noises at low speeds drive around a parking lot (or the street, if it isn't busy) and have someone outside walk along side and listen at each corner
2) lift up the rear end (in 2WD) and put it in gear to see if it makes noise when the tires spin (use jack stands! be sure to stop the tires with the brakes before putting in park!).
3) Lift the front and put it in 4WD, disconnect the rear driveshaft at the output yoke and put it in gear (see notes about brakes & jackstands!).
4) Get a passenger to ride in the front/back seat to listen to the noise

JW

[ddewar53]

01xjkid said:

Snip

Rear ds is solid, doesn't rotate or shift when in park

Snip
ANY suggestions would be greatly appreciated
Thanks,

Nick

When parked and in gear there is usually tension on the rear d/s, so even if there's a bad u-joint it will feel tight. Chock the front, raise the back, support it on jackstands - it neutral. That will let you spin the d/s and observe the ujoints thru complete rotations

[RedLightRubi]

Thanks guys, i am glad the consensus is u-joints. I will do the "Jon" method to see if there is any play in them. Could this be rear brakes? my drums have been going for a while and i have just been waiting to source a ZJ to convert mine over to disks.....

Thanks again
Nick

[Jon W]

If it was rear brakes you should only hear it when you apply brakes, unless something is really broken/dragging. I wouldn't expect it to matter if you were on the gas or not though - the dragging would be constant.

JW