The Shop > Axle / Differential

Thump and Klunk

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MIPS:
Starting about three weeks ago after I switched to quieter tires I began to hear a thumping or klunking from the back end that while driving under all city/highway conditions would come and go. I can't really say for sure if it's more prominent turning left or right either. The only real reason I'm being overly concerned right now is I'm about to clock something like 10000km in the next two months travelling to various computer shows and if it's gonna fail, it's going to do so rapidly and when I won't have the resources to get it fixed.

Raised the back on jackstands but couldn't replicate or hear anything, so it wanted the wheels to be loaded. Sounds like the noise is on-time with the rotation of the wheels, so that rules out a pinion bearing again.
Since I got the car I've had the rear-end serviced exclusively by one transmission and axle specialty shop. We've already replaced the pinion bearing, the wheel bearings, one axle shaft and fully serviced the entire differential assembly probably five years ago. I had it taken in earlier this week and we found the fluid was black but did not contain any metal. We also found the U-joint was bad so we switched that and the noise seemingly went away.
Well it's back this morning after being quiet for the last three days. Not as bad since I guess there *was* some U-joint noise making it through but the noise still comes and goes.

I'm probably going to put another 1000km on the thing before I make the first leg of the trip but as the travel date gets closer I'm getting more nervous because I can book the car in for work but it might take days to either see it or get parts to repair whatever the issue is. I'd like to nail this one down early.

vangremlin:
Good luck and keep us posted on the resolution!

MIPS:
I'm curious if there's anything else you want me to test beyond "wear it down some more" in an attempt to make it more consistent for troubleshooting purposes like go out for a long drive. Other than waiting for it to fail there's the nuclear option of changing axle and differential bearings but that's not a fun job if that's not the issue.

djm3452004:

--- Quote from: MIPS on June 14, 2024, 11:44:24 AM ---I'm curious if there's anything else you want me to test beyond "wear it down some more" in an attempt to make it more consistent for troubleshooting purposes like go out for a long drive. Other than waiting for it to fail there's the nuclear option of changing axle and differential bearings but that's not a fun job if that's not the issue.

--- End quote ---


If it were me, I'd start simple and cheap -- pull the wheels and drums to see if anything seems obviously amiss.  It could be something simple, like a brake shoe hold-down spring or something has failed. 

You'd get to see where the axle passes through the seal and see if an uneven wear shows up on the shaft where it passes through the seal, then push/pull on the shaft for abnormal end-play, and twist the hub-end back and forth to make sure that the splined mating between the hub and shaft is good.  If you suddenly got 20-deg of rotation instead of the normal <5-deg, well, obviously there's a problem in the axle internals.

While you had everything jacked up, and tires still on, you could take a gloved hand over the tread surface of the tires while spinning the wheels to see if any high spots are present, implying that a belt in the tire could have failed.

I wouldn't consider tearing into or changing an entire axle out entirely until I had done some very simple checks first.

Good luck diagnosing...

David

MIPS:
Well doubting myself, I put it on jackstands again and this time took took the wheels and the drums off and with it in Drive and taking turns holding one hub or the other from moving I crawled under the car and with a stethoscope checked every seal point, bearing and multiple points around the differential housing to hear if there was anything that even with no load could explain the noises.



Nothing. It all sounds fine. What I did however discover when I pulled the passenger side drum off was a snapped adjuster cable. Could that be sounds I was hearing? No idea. The pads still had lots of meat on them but it looked like it had failed a while ago. Replaced the cable. Adjusted the brakes and put it all back together. Push/pull and radially wise there was a bit of play, but I would not say an excessive amount. Note the clean looking differential cover. The shop's inspection had them in there and they too didn't note excessive play.



(Ignore the wetness. I rinsed it all down with water and that's not actually a leaking cylinder.)

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