I've been getting a little noise out of the rear axle. Varies on engine torque (accel/coast/deccel).
So I took the rear driveshaft off. And the rear u-joint was a little notchy on one of the directions. Cardan joint was perfectly fluid and fine. So about 40 minutes of tapping/hammering/etc with a couple of sockets of different sized and replaced the u-joint.
Then I spun one of the wheels with the driveshaft off. There's still something going on in there. I don't think it's the wheel bearings, they were replaced only a year ago (5K miles?) and while it's possible they were damaged on installation (if the machine shop pushed on the outer race, for example) this sound seems to be coming from the differential. Possibly from the pinion bearings. No leaks, full of oil, no perceptible slack in the pinion bearings at all. But still, it's a grumbling sound when one wheel is spun.
I didn't want to mess with that right now, so I put the driveshaft back on. Drive it around, the stiff u-joint (brinelled bearing surfaces on the arms the diff side) was apparently making *some* of the noise. But some remains.
I got *SUPER* lucky a few months ago at a pick-n-pull and managed to snag a locker diff for super cheap. Plans are to look that over *very* carefully and decide on getting it rebuilt or not, then swapping it out and making my noisy one the 'emergency backup' diff.
Spent the weekend swapping rear differentials.
I was rotating the tires and with the wheels off, crawled around underneath and listened to the original diff a bit more carefully. Definitely a bearing noise from the pinion. Still not the slightest perceptible slack in the bearing, but a definite rumble, one that coincides with the noises it's been making while driving lately. The new u-joint I replaced a couple of weeks ago helped some, but it still wasn't good.
So I looked over my junkyard diff, trying to decide whether or not to have it rebuilt before installing it. Gears looked great, more importantly, gear lash seemed to be nice and tight. While this diff wa a bit oily on the outside for some reason, there wasn't any real sign of oil coming out of the pinion seal.
So I decided to just put it on as is. I had the usual amount of salt-belt grief pulling the old diff out of the axle housing - most of the studs pulled out of the housing, but one of the ones that remained (not one of the two long ones that hold the locker actuator on, though) was being a PITA. I did remember to lock it first - the diff won't come out of the housing in the unlocked position, and it's nice to have the actuator and diff in the same state for reassembly.
Then lots of scraping on the axle housing and new diff to remove the old gasket.
My junkyard diff came without an actuator - someone had visited it in the junkyard before me and snagged that (but not the diff???) so I had to swap it over. I thought I was being very careful, but... I cracked that back plate. It's ridiculously easy to do. Fortunately enough, it isn't actually that structurally significant, since the outer housing bolts down on top of it.
Either way, I thought I really should take it apart to check for water damage - it was nice and clean inside. No signs of water entry ever. Just some dried looking grease. I cleaned that out, added fresh lithium grease, and cleaned the mildly cracked back plate really well and used some JB-Weld on the cracks to (hopefully) keep water out in the future. Then reseated the o-ring with a little RTV and put it all back together.
And now? No more geary noises while driving, either accelerating or under engine braking. Nice and quiet. In retrospect this really has been making noises for a very long time, perhaps 10 - 15K miles? It just sort of started slowly and quietly, and I sort of got used to it making some gear noises, it only very slowly got to the point where I finally perceived it as something wrong. Since the pinion bearings still have no apparent slop in them, they'd probably still last 10's of thousands of miles more.
We'll just keep it as an emergency spare. Since it's possible we won't need it, no point in spending $$$ having it rebuilt, it would work in a pinch.
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