When Im cruising going over 45mph and I let off the gas a little there is a slight clunk coming from underneath. Once I give it gas just a little there is a clunk again. My gas pedal is like a clunk button. There is also a howl coming from underneath when I am going over 60. I just had my bearings redone in my diff and axles. I am leaning toward slip yoke issues or u joints. None are very expensive. What do you guys think?

 

U-joints or bad tranny/motor mounts are typical of drivetrain "clunk" noise.

Loose shocks can give you a wheel area "clunk" noise.

Poke your noggin under there and see what's loose.

 

Shocks are new and torqued to spec. Replaced the tranny mount already with engine mounts on the agenda for this weekend. Thanks.

 

Since the clunk is at speed, in conjunction with a higher speed howl. My bet is a rear drive-shaft u-joint, and most likely the rear most u-joint. They tend to howl under acceleration/load as they get "dry" and begin to wear and fail.

 

I will probably do both u joints on the rear shaft in the next few weeks. A pretty cheap endeavor. I love the XJ. I am a bit of a glutton for punishment, so always having something to wrench on is perfect for me. Cheers.

 

I think that is a loose pinion bearing. put a socket on the rear pinion nut and see if you can budge it. the spec is over 200 ft lbs so you shouldn't be able to. Not too much, just a little, see if it helps. You or your rear diff rebuilder should know what you're doing before you get too far into that one.

 

Literally just had all diff bearings and axle bearings done two days ago by the best shop in town. The particular symptom im describing was there before and after the diff job.

 

I would pay them a call, likely they will want to be more than helpful

 

Go underneath with the jeep in gear but not running and grab the driveshaft and turn it back and forth by hand. you will be able to see the lost motion either in the u joints or in the rear end. Do the same for the front driveshaft. The next step is more dangerous...get someone you trust to step on the brakes hard ..with it running ...and then shift in and out of gear with you looking at the whole drivetrain to see what might be shifting. Also check that your sway bar end link bushings are not worn and that the studs are not loose

 

The clunk and howl might be two separate parts. I think the clunk can be anything suspension or driveline related. The howl, however, especially with it becoming more prominent at higher speed, is most likely driveline. Since the rear diff has just been redone, I am leaning toward u joints.

 

Re: the howl:

An easy check is to pull out the rear driveshaft and take a quick drive in 4wd. If the howl goes away, you know you've isolated it to a rear drive line. If it's still there pull the front driveshaft and repeat the quick test drive. If it goes away then you know it's front drive line related.
It may very well be that you pull the rear driveshaft off and it will be very obvious that one of the u-joints is bad.

It could be the case that the nice and tight new pinions caused the worn u-joints to finally give out - however don't completely discount the possibility of something not having been done correctly on the axle rebuild.
If it were me, I'd pull the driveshafts and do those tests as I mentioned since they're pretty easy and quick tests and I'd lean toward the tight pinions causing the worn u-joints to give out. Also just because the howl goes away if you pull the shaft, doesn't necessarily mean it's in the removed shaft - the less force on the moving parts can prevent signs of failure to be reduced.
If you find that the u-joints are nice and tight and rotate smoothly, I would not hesitate to return to the shop that did the axles and talk to them about it. Even a good shop can have a bad day or a new employee that causes a mistake - fortunately most shops do care that their work is sound and will usually work with you to resolve issues.

The clunk should be pretty straightforward to diagnose if you follow the advise given by others in this thread.

 

Great suggestion about isolating the shafts. However, I have the rare and highly coveted 4x2 XJ (main reason for diff job: eaton truetrac install). If I disconnect my rear shaft I will need an oxen to pull me. Seriously though, the symptoms that I described were there before and after the diff job. No change what so ever. When they had my stuff apart they said everything looked perfect. I was surprised because I thought it was all in the diff. oh well. This weekend will be a matter of swapping in a fresh set of u joints and shaking all the suspension components and see what clunks.

 

The reason I answered with the details I did, is because I chased the same symptoms for a while. They came on right after I had added a brush guard to the front. So of course, for a few weeks I was convinced that the "howl" had to be wind noise or vibration coming from the brush guard and its mounts. It took a while to rule all of that out. The ruling out eventually lead me to the rear driveshaft, which I had just rebuilt 1 year prior. So I didn't immediately suspect the u-joints. Also, I had gone under and shaken the joints around, and there was no play whatsoever, and no external indication of problems. I also had one of my trusted shops take a look to rule out the u-joints and perhaps exhaust leaks. They found nothing out of order either. Eventually the troubleshooting narrowed it down to something in the rear driveshaft (I did remove the front shaft as part of the test). So I dropped the rear shaft, and sure enough...a single cap on the rearmost u-joint had suffered water/salt intrusion and had run dry (grease was missing/compromised) and it was just starting to chew itself into dust internally. Because it was just 1 of the caps, and the other 3 where fine, the joint had no play and no external signs of failure. Replaced the joints, and problem was solved.

The reason the cap had gone dry? because when I first rebuilt my drive shafts, I had used serviceable joints, where the grease fittings were nearly impossible to reach (the kind where the fitting is down near the center of the u-joint), so I was having a hard time lubing them during normal maintenance routines. I had to use a special grease gun fitting, that wasn't really allowing me to push the amount of grease that I wanted to, and not with enough pressure. Without enough grease getting into the joint during servicing, it was not pushing out the water/salt that had made its way in to the bad cap. So when I rebuilt the shaft, I switched to HD style u-joints that have the grease fitting on the cap (instead of down near the body), so that I can grease them properly now.

I hope your problem ends up being as simple. Because in the whole scheme of things, a bad u-joint is one of the easiest, cheapest, and quickest things to deal with on the drive line.

 

Again, if you just paid a reputable shop to rebuild the rear end, I cannot see why not go back there and ask them what they think the problem is, whether it's the rear end or not they should be glad to help you.

 

Did you by chance, have the shop add shims to your rear end to solve a problem of too much angle, after you installed a lift on your XJ?