Need Opinions On Front End Noise

[M4Madness]

I took my '96 XJ to a very reputable differential shop to have 4.56 gears installed. Upon picking it up, I immediately noticed a strange knocking/thumping noise emitting from the front end area as soon as I pulled from their parking lot and took off down the road. The sound was definitely rotational and not caused by random bumps in the road. The sound speeds up or slows down in relation to vehicle speed, and is most noticeable at slow speeds while coasting.

I returned to the shop and the shop's owner and I inspected it. He has complete hearing loss in one ear, and cannot hear it. He had replaced one of the axle u-joints, but aid he felt the other u-joint and hubs were good, but perhaps they were causing the sound. I changed the remaining u-joint and both hubs today, yet the sound still persists. The sound was definitely not present when I dropped it off for the work. I see nothing rubbing as far as brake hardware goes. The sound is the same in both 2WD and 4WD.

He did say that he had a hard time removing and installing the front driveshaft, as though it was too long. It is the factory driveshaft. Could he have damaged something regarding the front driveshaft? I may pull it tomorrow to see if the sound disappears. The only other thing that comes to mind is that he mentioned that the master install kit I bought from Just Differentials for the D30 had the wrong bearings and he had to swap them for correct ones.

Any suggestions before I have a nervous breakdown? LOL!

 

[joe_peters]

Does this one-eared guy do a lot of XJs?

This post sounds very similar to one I read before.

When did this happen?

EDIT: yep, very familiar: http://naxja.org/forum/showthread.php?t=1021771&highlight=complete+hearing+loss

Probably would be better to revive the original thread rather than start a new one.

 

[M4Madness]

Does this one-eared guy do a lot of XJs?

He has probably done hundreds of D30's. With 30+ years in this career field, I'm sure he's regeared every type of differential we could imagine.

This post sounds very similar to one I read before. Probably would be better to revive the original thread rather than start a new one.

I'm surprised it didn't get moved to this forum initially, as it seems to be considered an OEM topic. Better to start a new one in the correct location than to revive the incorrect one. Short of dropping the driveshaft, it seems that I've already followed every bit of advice given in the old thread. And tomorrow when the driveshaft is lying on my garage floor, I am out of ideas if that isn't it.

 

[joe_peters]

Well, post back tomorrow and we will see.

Good luck.

 

[M4Madness]

The front driveshaft is out, and the sound is still there.

 

[joe_peters]

Grab four good jack stands and put your XJ up on them.

With the front DS still out, a 3' length of vinyl tubing about 1/2"~3/4" ID, crawl under there while a trusted friend runs the engine and shifts through the gears.

Do I need to warn you to avoid getting tangled in moving objects?

Use the tube stuck in one ear to see if you can isolate the sound source. If the sound is not present, then reinstall the front DS and repeat the process.

This is a do-it-yourself project, not something we can help isolate for you. Once you have a general area isolated, you can switch to a mechanics stethoscope to try and pinpoint the source.

Good luck, post back with what you find.

 

[M4Madness]

I called the gear shop today and explained to the owner that the sound is still present. He wants me to bring it up there possibly Saturday. He has listening devices that clip under a vehicle to pinpoint a sound's source, and wants to attach one to each end and center of the front axle. It's a 2-hour round trip to his shop, but I'm out of ideas.

 

[1990heepxj]

i have a kind of clunk noise comin from my front pass side axle u joint but i can visibly see its dead

 

[M4Madness]

UPDATE:

The XJ was at the gear shop for one month today!!! The owner worked on it between other jobs, and checked everything he could possibly think of. The gears are Nitro brand, and he felt that they appeared to be of good quality. He checked for ring gear and carrier run-out with a dial indicator in about ten different spots, and found none. He removed the ring gear and visually inspected it under a lighted magnifier, and found three shiny spots on the teeth -- two on adjacent teeth and the other on a tooth two over from the others. He felt that they were high spots and rubbed them down some with emery cloth.

He got it back together again this morning, and called me to come up and test drive it with him. The sound was somewhat more quiet than before (perhaps his emery cloth?), but not gone by any means. With the microphones attached, the sound seemed more prominent near the driver's side axle end, but was also present on the microphone attached to the "hog's head". You could watch the knocking sound on the series of lights on the listening device, and as speed was increased, more lights would come on.

We both just finally called it a day and admitted that the thing has us beat. He said that perhaps the shiny spots on the ring gear were imperfections and they'll wear in with some mileage put on them. I told him I'll give it until mid to late summer, and if the sound persists, I'll just break down and buy a new set of gears and have them installed.