View Full Version : Popping/Grinding when flexing

September 19th, 2017, 17:42
Haven't been on NAXJA for quite a while. My Jeep has been down for a few years. Got it back up and running.

My setup:
94 XJ 4.0

RE 3.5" Super-Ride
Shimmed rear axle
TC drop about 1"
Stock tires for now

So I don't wheel a lot. Especially lately. I just replaced my rear bushings for my leafs. Once I got it all back together, I took it to a local off-road area to make sure all the clunking was gone. When my axles flex while driving (significantly more than just pulling into a driveway if that makes sense) I get a terrible grinding/popping noise. At first, I thought it was only when in 4wd, but noticed it was in 2wd too. It happens when I hit the throttle and just coasting (going down hill). I'm kind of at a loss for what it is. I've searched the forums and read about the TC slipping in and out of 4wd and grinding, but I don't think that's the case for this.

BTW, it did it before I replaced the bushings as well. Just figured I'd try to get it fixed now rather than before since I was super broke.

Any help would be greatly appreciated.

September 23rd, 2017, 11:04
Let's see if this works.


September 23rd, 2017, 13:56
I'd jack up the front axle and check ball joints and wheel bearings.

September 23rd, 2017, 16:42
Since the noise happens in 2wd and since front wheel bearings are rather unlikely to make any noises like that, they do not seem like logical source of the noise. Ball joints are a could be suspect, but the rhythm of the noises seems too fast to be ball joints.

Are the noises totally random, or do they relate more to when the Jeep flexes on the terrain, or more to when pressing or releasing the gas pedal ?

Inspect carefully at the transfer case and axle yokes for signs of faulty u-joints and/or contact between the yoke ears. Inspect for contact between the axle shaft and the exhaust. Inspect the motor and transmission mounts for excessive movement or failure. Confirm that all the suspension nuts and bolts are correctly torqued.

September 24th, 2017, 14:13
Front wheel bearings are good. Ball joints are good. Tim, you're correct that there is a rhythm to the noise. I believe it's proportional to the speed I'm going as well. Not positive since I don't normally go over un-even terrain at random different speeds. Normally fairly slowly.

The noises only occur on uneven terrain. I don't have any issues on flat roads or even dirt roads with pot holes. Only on the trails. The noises happen whether I'm going up hill or coasting downhill on uneven terrain.

The u-joints are all good. Checked them when I replaced the shackles and bushings. Checked the front when I greased the front end. I'll look for signs of binding on the yoke ears. Exhaust/axle area looks good and clear. I'll have to figure out how to check the motor/transmission mounts. Any ideas?

It feels like it's either the transfer case or in the rear end. I pulled the diff-cover off when I fixed the rear end and it didn't show any signs of extreme wear or any missing teeth in the pinion or ring gears.

There's 168k miles on the Jeep if that helps.

September 24th, 2017, 14:16
Is your sway bar hitting your front coil springs by chance?

September 24th, 2017, 14:21
Not that I can tell.