Squeak / Chirp in Rear Axle Pinion (Differential)

[98SurplusExpy]

Some background ... I took the truck into a shop and had a bad set of pinion bearings replaced. The shop did not get the preload right (too loose), and I had a decel noise in the rear end. The preload was tightened, and the noise went away.

After about a week (and after a towing trip), a new noise showed up. This time, it's a squeak / chirping sound. At first, I swore it was the brakes; however, after jacking the rear axle up and running the truck in drive, the sound was pinpointed at the rear axle pinion area.

The noise only occurs on decel after the pumpkin has warmed. I can let off the pedal and the squeak / chirping sound will start at a frequency thats relavent to the drive speed.

I suspected the drive shaft carrier bearing, but it was quiet. I also suspected the u-joints (a typical source of squeaks), but I replaced all of my u-joints with Spicer's (5-801x's) less than 10k miles ago.

Has anyone else had an experience with this sort of noise out of a 10.5" Sterling (or any other diff)? Should I replace the rear joint "again" or tighten the preload just a tad?

[Karls03]

The last time I had a rear end making noise, the pinion and ring gear were WAY too tight. Given that the pinion bearings were replaced, which means the differential came out, its possible that they didn't get the right wear pattern as well as the wrong pre-load.

BTW, how are you measuring the pre-load? Typically its done by checking the amount of torque required to rotate the pinion after the pinion nut has been torqued. I don't know about a 10.5, but I know a 9inch is around 10 inch/lbs. I also know that on a 9 inch you're not doing this with the r&p engaged.

I'd pop the diff cover, spray excess out with carb cleaner, dry the ring gear off and apply either Pershing Blue or ring and pinion marking compound and check the wear pattern. If its too tight, someone would be buying a new r&p on their shop dime. Even when we loosened up that 9 inch, it still screamed. Re-adjusting yours may have the same negative results, ie the damage is already done.