accel

I have an 01 XJ with a 4" lift and it's making a popping sound when I accelerate from a stop in 2WD. I noticed that it only does this when the wheels are straight or turned to the right. It sounds like a pop pop pop and then stops once I am up to speed. it almost sounds like something in the diff. if I accelerate lightly (1500 rpm) it doesnt make the noise, but if i get on it a little (2500 rpm) it sounds terrible.

From searching this forum I found the most common symptoms:
1) a gear tooth in the diff is chipped or missing
2) front axle u-joints are worn.
3) driveshaft u-joints are worn.
4) transmission mount worn

1) I popped both diff covers and inspected the ring gear, pionion, side gears, and spider gears. The rear (chrysler 8.25) has wear patterns but nothing is broken or looks damaged. the truck has 160K so it seemed normal to me. The front (dana 30) doesn't look as worn, and it too had no signs of damage. the fluid in both was pretty dirty but I didn't see any chunks of metal. Put new fluid in, problem still there.

2) I replaced both sides, and one side was bad. when I took the cap off the u-joint a bunch of dust and rusty broken needles came out. I thought this was the problem but after installing new u-joints on both sides, it still makes the same noise when accelerating and turning.

3) I did new u-joints on the rear shaft and pulled the front drive shaft out (i didn't have the parts to rebuild the double cardan). Problem is still there. I don't think it has anything to do with the front shaft since I took it out.

4) I didn't replace it but it doesn't really look worn. To be honest I don't really know what it should look like, but i'm tired of replacing parts and still having the same issue. Will it look obviously damaged if it is worn? the transmission looks straight from side to side and the rubber looks in tact.

I dont think it's ball joints because the wheels dont move up and down when it's jacked up. I replaced the sway bar bushings about a year ago. It's a new noise that only happens when I take off from a stop. I'm running out of ideas.. any help would be appreciated, thanks guys.

Liquid Iron Ind.

Check your track bar. if its an after market one. i had the same issue with the superflex joint in mine.

DFlintstone

Btommy

I too have this problem, I just posted in another section of CF looking for answers. I just replaced all ball joints both u joints all tie rods track bar, all bushings in front end (whole new front end basically) and drove to work today and the same damn thing happened. I am very frustrated by this.
please post if you find the problem.

accel

I did the lift myself, it has 2" old man emu springs with 2" spacers and a lift shackle with an s10 bastard pack in rear. 1/2" Tcase drop. Bilstein 5150's all around. Everything else is still stock (for now), including the trackbar, pitman arm, swaybar end links, control arms, etc. I get slight driveline vibrations over 60 but otherwise it feels fine. I didnt notice this problem after lifting though, it only started happening recently. Not sure if it is just a coincidence but i noticed it after the last i took it out on the beach. 4lo and i pushed it a little but nothing terrible.

Is the trackbar an issue only if it is aftermarket? I haven't touched mine at all. I thought about redrilling the hole to center the axle because right now it sticks out on the drivers side about 1/2" more than passenger side, but it doesnt really bother me. I also thought about getting an aftermarket one for a 4" lift. what does a bad trackbar look/feel like?

I guess my next step will be to check the t-case fluid for metal? could i have damaged a gear in the t-case? I have the np231 (part time only). I don't really know what it looks like inside and I'm not dying to pull it out since its my DD and i need it to get to work. If it's common for the t-case to fail then i guess i'll be pretty busy this weekend..

spazzyfry123

With any lift you should have an adjustable track bar to recenter the axle. If you're not getting a decent vibration at speed, it may not be the culprit of your issue, but should still be addressed for alignment reasons.

For whatever reason, a TJ's track bar is the only thing I can visualize. A bit spot to check is where the ball joint at its end meets with the frame (or "frame" in this case). Have someone turn the wheel back and forth while you watch this joint for excessive play.

Another thing I would check is any tie-rod ends. Those will definitely make a distinctive popping sound from it sliding on what used to be threads.

A dropped pitman arm may be in need as well... Steering angles are all out of whack with 4" of lift and using factory steering alignment components. Replacing a tie-rod now could be a band-aid fix when the reason they're going bad is from bad steering angle.

accel

Thanks for your help guys. I think I figured out my problem. I pulled the rear driveshaft and drove it in 4 wheel drive (effectively making it just front wheel drive) and the noise is gone. It didn't matter how hard I hit the gas or how much I cut the wheel, the noise just wasn't there anymore. So I either have a bad driveshaft or its my rear. Based on the fact that I pushed it kinda hard last time I went on the beach, I'm betting that I chipped a tooth on the pinion gear, especially since this is the one gear you can't really see when you pop the diff cover since its behind the carrier.

Thinking about it, it kinda makes sense since I only hear the noise under accelerating when the ring gear is being driven by the pinion, but not when it coasts or in reverse when it uses a different side of the gear. I'm still confused as to why I don't hear it when making a left turn.. i guess with the weight shifting it changes the load which changes the noise?

I'm just glad its not my t-case or tranny. The good thing is now I have a good excuse to regear to 4.11s Now if only this was easy to do....

DFlintstone

"chipped a tooth on the pinion gear'......

I think that pinion is always pretty busy. It's those spiders that run around when your getten jiggy with it.

lgnut123

This was a few months ago but what was the conclusion? I am having the EXACT same problem you explained in the original post. No noise when coasting or up to speed, only when accelerating from a stop. The noise sounds like its coming directly under the center console and can be felt in my feet. 97 Cherokee Sport with NP 231 Help?