Clunk sound after u-joint replacement

[Don Bulee]

Hello, I think I need help here... I recently regeared my jeep (5.38s on 35 are just awesome) and after one week or two a clunk sound started, I took it back to the shop and they told me that some debree got cought inside my oem rubi locker and that was the issue.. but after cleaning all was good again.. once it was in the shop I bought the spicer u joints for my 2.5 year old rear adams driveshaft just for the sake of having everything new, (I added a new front Adams driveshaft to eliminate vibrations as well) and when I took it from the shop it was just fine, I took a small road trip (300/400 miles) and it was just fine.. but when I was arriving to my home I started hearing a new clunking sound (two weeks after the last time it was on the shop), I took it back to the shop, they opened the diff and they told me everything was just fine, that it was probably the tranny skid being too up and the angle of the driveshaft was causing the issue, I do have a small tummy tuck (with Rough Country high clearance skid plate, like 2.5 inches taller than OEM), but I have the DC driveshaft, the MML and the adjustable rear upper control arms and I have had that set up for years without any clunking noises, so I thought the angles was not the problem, even tho, the shop added some spacers to the tranny skid, to lower the trasnfer case, and the clunk sound went away!!! so... not sure what is the problem... I didn't change anything from my angles (rear control arms nor skid plates), just replaced the u joints in my rear driveshaft, and I don't get why a transfer skid spacer would eliminate the clunking noise... so..

- maybe the CV centering yoke is bad?
- the new gears could have changed anything?
- why would the clunk sound start two weeks and 400 miles after leaving the shop?
- I can hear the clunk noises more clear when I'm going uphill or when I'm applying stress to the drivetrain, once I get some speed the clunk noise is less hearable
- My tranny mount is in good shape
- there is NO vibration at any speed, just the clunk noise, I was driving 75-80mph without any vibration

thanks!!

 

[Chris]

Hello, I think I need help here... I recently regeared my jeep (5.38s on 35 are just awesome) and after one week or two a clunk sound started, I took it back to the shop and they told me that some debree got cought inside my oem rubi locker and that was the issue.. but after cleaning all was good again.. once it was in the shop I bought the spicer u joints for my 2.5 year old rear adams driveshaft just for the sake of having everything new, (I added a new front Adams driveshaft to eliminate vibrations as well) and when I took it from the shop it was just fine, I took a small road trip (300/400 miles) and it was just fine.. but when I was arriving to my home I started hearing a new clunking sound (two weeks after the last time it was on the shop), I took it back to the shop, they opened the diff and they told me everything was just fine, that it was probably the tranny skid being too up and the angle of the driveshaft was causing the issue, I do have a small tummy tuck (with Rough Country high clearance skid plate, like 2.5 inches taller than OEM), but I have the DC driveshaft, the MML and the adjustable rear upper control arms and I have had that set up for years without any clunking noises, so I thought the angles was not the problem, even tho, the shop added some spacers to the tranny skid, to lower the trasnfer case, and the clunk sound went away!!! so... not sure what is the problem... I didn't change anything from my angles (rear control arms nor skid plates), just replaced the u joints in my rear driveshaft, and I don't get why a transfer skid spacer would eliminate the clunking noise... so..

- maybe the CV centering yoke is bad?
- the new gears could have changed anything?
- why would the clunk sound start two weeks and 400 miles after leaving the shop?
- I can hear the clunk noises more clear when I'm going uphill or when I'm applying stress to the drivetrain, once I get some speed the clunk noise is less hearable
- My tranny mount is in good shape
- there is NO vibration at any speed, just the clunk noise, I was driving 75-80mph without any vibration

thanks!!

View attachment 654998

Here are a few things to check:

1. It's definitely possible that the CV centering yoke could be bad or worn, especially if you're experiencing a clunk that gets pronounced under load. If it’s not centered properly or if the bearings are worn, it could cause noise when the driveline is under stress. Consider giving the CV a visual inspection and check for any signs of wear or play.

2. While re-gearing usually shouldn't cause clunking noises, the new setup could put different stresses on components than the original gearing. If the gear backlash isn't set correctly, it could potentially lead to noises, but you'd typically notice vibration as well. Since you mentioned no vibrations, it might just be a coincidence.

3. The fact that it started two weeks and 400 miles after the shop work could indicate that something was disturbed or that a component was developing play or wear that just happened to surface after driving for a while. It might be worth checking all the hardware around the rear end, driveshaft, and the newly replaced u-joints to ensure everything is properly torqued and seated.

4. The lowering of the transfer case via the skid plate spacers could very well have helped reduce the angle on your driveshaft, which might have improved the alignment just enough to eliminate the clunk. Sometimes, tiny adjustments in angle can have significant effects, and it’s possible that your setup was on the edge before the change.

5. Since you mention that the clunking is more pronounced when going uphill or under load, this often points to something either binding or potentially loose. Check all the mounting points for the driveshaft and any associated components.

 

[Don Bulee]

as always, thank you Chris!