Differential clunk noise in reverse

[norske]

Lifted the bed off my 68 Chevy c10 and decided that's the best time to change the pinion seal, change the differential fluid, and check u-joints. The pinion seal appered to be leaking, so replaced it. All the u-joints were no good, put in all 3 of them. It's a 2-piece driveshaft with the carrier bearing (that was ok). The rear end is a 12-bolt with 8 7/8" ring gear, says GM56 on it. Talked to a guy who works on the local dirt track circuit and he said there was no preload on the pinion nut, just rattle it back on. When I got finished, backed it out of the shop and noticed the rear end (I think) seems to bind and "clunk" in reverse. It doesn't do it going forward. I don't know if it did it before or not. There was just the nut and washer on the pinion. Could I have done something wrong (There is a preload on the pinion nut?) or maybe a problem that I just didn't notice before? Going to jack it up and spin the wheels and see what's up. Any ideas appreciated.

[neba]

bad advise from local gearhead. there are books full of information on what is needed to check wear patterns, shim, and torque to specs.

[425HP409]

Ditto, bad idea from gearhead. You must install the pinion nut EXACTLY in the same place that it was before to prevent problems. When it was installed, it was torqued to crush the crush sleeve on the pinion shaft. You must put the nut back on to have the exact preload that it originally had. If it is too tight, you will demolish the pinion bearings. If it is too loose, you will have slop in the pinion, which will demolish the ring and pinion. You may try to tighten it up so that you just eliminate the slop in the pinion, front to back. Good Luck

[cdowns]

the factory solution was called a service manual//availabe at very cheap prices from most board vendors

[norske]

It absolutely makes sense that a tight nut would wreck the bearing and a loose nut would wreck the gears. Think I'm going to back it off and take out the slop and call it good. We'll see if the binding stops.

[LONGHAIR]

As much as I always advise that people not mess with rear ends, it is doubtfull that you really screwed-up anything doing this. Simply removing the pinion yoke and swapping the seal should not cause any major issues. The pinion bearings are indeed "preloaded" and that "adjustment" is controlled by a crush sleeve. These crush sleeves are notoriously hard to crush, more-so when they are new, but even after being "set". Even if you did over-crush it, that would not cause a clunk, it bad (potentailly very bad) but not a clunk.

At this point "shims" and "wear patterns" are a moot point. Those things are already set and cannot be changed. That's a "one time" deal.

Pop the cover off of that thing and have a look inside, post pictures if you have questions about what you see....

[Shaky]

My buddy had a reverse "clunk" in his '69. Turned out to be a rusted out U-bolt for the trailing arm. It failed on I-95 during rush hour.

Check your arms first and then go to the rear. Oh yeah, that gearhead advice was not good...

[norske]

Ok, I got it. That nut goes on hard, I didn't have it up there tight enough. Tightened it up to the crush sleeve, then bumped it back until there was just a hair play. she's nice and quiet now.