65 Suburban Posi Noise When Hot - Additive Didn't Help

[RoyL]

Sorry, this seems to have discussed in several places, didn't want to tag onto an old thread, but bring what I read to my situation and see what I can learn.

Had the Burb since January. Got her running and have been taking short trips checking things out. Didn't notice the noise until after a longer trip. After reading several similar threads here and elsewhere, my posi noise sounded typical, "clunking" when turning from a stop or turning at very slow speeds. The clunking is pretty severe, feels like the rear end is gonna fall out. I tried the most recommended solution: Add the posi additive and the noise will go away. So I drained the diff, added the gear oil (80w-90) and the posi additive (generic at OReilly's). I saw no metal shavings in the diff oil when I drained. Thought that worked but once it got up to temp, the noise was back. Tried circling around in a parking lot left and right turns to "work the lube in?" No help.

What do I try next, before taking to a rear end shop? Axle bearings?

Thx,
Roy

[pmkrew]

GM diff. additive, I've heard the generics don't work...

[RoyL]

Originally Posted by pmkrew

GM diff. additive, I've heard the generics don't work...

pmkrew,
Thx, was wondering about that. Read some threads where guys said the generics worked fine, some even said the Ford stuff worked better . . . Some say just go with synthetic and no additive. Worth a try . . . Roy

[RoyL]

Originally Posted by RoyL

pmkrew,
Thx, was wondering about that. Read some threads where guys said the generics worked fine, some even said the Ford stuff worked better . . . Some say just go with synthetic and no additive. Worth a try . . . Roy

Well, glory be . . I drained the rear end and added the GM stuff and drove her for a good long cruise, and turned into a parking lot and did slow circles and turns from a stop and SOAB, she's 90% quieter . . . still got some lesser clunks when backing up turning. Guess those GM chemists know what they are doing. GM parts guy said half the guys that buy it are Ford owners . . .

Thanks much!

Roy

[protrash64]

I owned a '90 SS454 and thats what was recommended for them also; GM additives only.