Rear Differential

[ramchuck]

I have a 2017 2500 Limited diesel. It has been well cared for and all services have been performed. Currently has 93,000 miles, and has done minimal towing. My issue is when the transmission downshifts there is a "clunk" in the rear end. I put the transfer case in neutral and you can rotate the rear driveshaft and see the "slop" in the rear end. There is no other noise, the diff lube looked good, so what do you think needs done. Can the differential be re-shimmed, or simply is it worn out and need replaced?

Chuck

 

[Dean2]

You need to locate the source of the "Slop". I would start with the U Joints, and check them for play. Then the intermediate/center support, bushing/bearing if you have one of those.

Hopefully it is one of those two because after that it gets expensive. If the slop is in the actual differential or the transfer case, you are going to need to open it up and locate the cause, most everything can be rebuilt if you know what you are doing or have access to a good shop. Let us know how you make out.

 

[62Blazer]

The normal and correct setup allows a certain amount of backlash/slop in the rear axle. It's hard to know if what you have is too much or normal, but point being if you rotate the rear driveshaft there is some slop.

 

[Gr8bawana]

If the "clunk" is relatively new it's most likely your u-joint.

 

[CanuckRam1313]

At nearly 100K Miles.... the front/rear diff fluid should be changed as well as the transfer case fluid, too.

I would also consider doing a transmission fluid & filter change as well. Your transmission will thank you!

As others have also indicated, check the play in the u-joints as these may be suspect parts that are aging

If it still persists, then as stated above, opening the transfer case may be necessary, too.

 

[mktowingservices]

The "clunk" you’re experiencing during downshifting could be due to wear in the differential or drivetrain components. The rotational play ("slop") you noticed in the rear driveshaft suggests possible wear in the pinion and ring gear, bearings, or even the U-joints. Re-shimming might help if it's a matter of adjusting tolerances, but if the gears or bearings are excessively worn, replacement may be necessary.

Since the diff lube looked good and there’s no noise, it might not be a complete failure yet, but it’s worth having it inspected by a specialist. They can confirm whether it’s just an adjustment issue or if more extensive repairs are needed.

Also, if the issue worsens or if you’re concerned about driving it, consider using a towing service to transport your vehicle to a mechanic to avoid potential further damage. Early diagnosis and action could save you from a bigger repair bill.

Have you noticed any vibrations or other changes while driving? Those could also help pinpoint the root cause.

 

[R.D.J.]

Believe it or not, I have seen and felt clunking when downshifting which was caused by cross leaks in the valve body. Momentarily, the transmission was in two gears at once.