Having this mystery sound. Only happens at slow and crawling speeds. Pushing the car slowly in neutral in video but happens in gear too. Had a worse but similar sound that went away when I centered the diff with an adjustable panhard. I am noticing the end of the yoke that goes against the diff housing is shiny and the rust is worn away (see picture). Cant see it in the video but the rear u joint and yoke shutter when its rolling a little faster. Could this just be an alignment issue or is my diff having possible issues?

video link: http://tinypic.com/r/709q2p/5

pic of yoke


Thanks
Matt

 

Wow, I don't know what that is. Are you sure that it is coming from the area of the yoke? Can you hold the yoke and move it up and down or in and out? If you have any movement other than rotation then you have a pinion bearing problem or the pinion nut has backed off.

 

I drove it over a jiffy lube bay and the sound was coming from the yoke area. but it is loud and thats just where it sounded like it came from. There isnt any play other than rotation from what I can tell

 

Brakes might make that sound if things aren't put together right.

Has somebody messed with your brakes lately?

 

ya sounds like pinion lash way too much, not sure if it would sound like that though. possibly the bearing but i cant see how a bearing would make that noise. my best guess would be a broken planetary (spider etc.) gear in the differential or some other part inside broke

 

The noise comes many times before the pinion makes one full turn, so I'm having a hard time thinking of something that would do that.

 

Thanks for the input. Maybe I'll take the cover off tomorrow and see if anything inside is worrying then. BTW its a BW 9 bolt if you cant tell by the video

 

Are both rear tires exactly the same size? Do they have the same amonut of air pressure? I noticed in the video that the front wheels are turned slightly. Does it make this noise when the wheels are straight? It sounds to me like the cones are popping in the differential. When was the oil changed last?

 

Both tires are the same size and pressure and the fluid is up to date. It does make the sound when the wheels are straight but it is worse when they are turned. maybe that's a clue

 

Did you use any of the GM limited slip oil additive in it with the new oil? If you didn't then try putting a bottle in and drive it a little. That might fix it.

 

I would think it has something to do with your limited slip. You really should take off the rear cover and you'll probably spot it right away.

That will keep you from having to guess.

 

I talked to a differential guy today who is supposed to be the best around. He said he thinks the carrier is messed up or broken. But he also said he can't rebuild the BW 9 bolt because he can't get a carrier or parts for it. So I think I will take your advice and open it up and change the fluid while I'm in there. As well as keep an eye out for used diffs...

 

I don't think anything is broke, and you can get parts for it. I think you just need to get the right oil in it.

 

Well I opened up the cover and put the new fluid in. The sound is still persistent. There were no bit of metal or shavings in the fluid. The fluid looked due but not that bad. Not really sure what else it might be now. Any diff or trans shops I call have never heard of this 9 bolt and says they cannot get parts or rebuild it

 

Did you use the GM oil additive? Give it some time. It might take a little while to get the oil additive into the cones.

 

I used castrol limited slip 80w-90 which i was told will meet the gm limited slip requirements without putting the additive. Didnt want to put too much additive in

And here's a video of the diff with the cover off (not real interesting): http://tinypic.com/r/30227mp/5

I forgot to but I should have checked the mesh pattern with grease while I had the cover off...

 

You are not following directions. Use the GM oil additive. Use ONLY the GM oil additive. Do NOT use any additive from the auto parts store. Use GM oil additive.

 

I'm fairly certain it is not a fluid related problem at this point and that this fluid will be fine if it meets the limited slip requirements. The fluid I just took out was full, a synthetic fluid, and had the gm additive in it anyway.

 

But I will put the additive in as a precaution if you think its fine to add to that castrol 80w90?

 

Yes, add it to what is in there. Give it time. It won't work right away.

 

Noise is gone! Look at me listening to these local so called "diff experts" telling me my gears are exploding, when all I needed was the good old third gen forum! The noise got better after I changed the fluid and went away with the addition of the gm friction modifier, thanks for all the help my car is now 100%!

 

I don't know everything, but there are a few things that I do know. I was pretty sure that the GM additive would take care of the problem for you. I'm glad it worked out for you. Now get out there and enjoy it.