Hi all,
I have a Nine bolt disc rear axle in my Z28. When I drive down the road say over 20 mph, it has a loud howling noise out of the diff. Ive taken the cover off, checked the axles and pinion for movement, and there was nothing in the oil as far as shavings or milkiness. Everything is tight, so my question is: Are these axles noisy from the get go? Or is it normal to have noise?

 

If it still has the factory gears (read no idiot replaced them) and no damage is on them sounds like you have a bad bearing.

 

Thats what I was thinking too. Thats why I checked for play and everything was tight. Im assuming its factory gears but the ID tag is long gone. I put it on stands and tried jiggling the pinion yoke, pulled in and out on the axles and all snug. To me it doesnt feel like a bearing, but ive never torn these down and Im nervous that its gonna go but no other signs point to failure.

 

Bad bearings don't always mean play, could be it ran low on oil and they got messed up. I would start with something easy check the wheel bearings before touching the pinion

 

To answer your question, they were not noisy from the factory. Something is wrong.

Could be worn bearings, or someone may have been in there and did the setup wrong.

From my experience, once the diff starts making noise, everything inside needs to be replaced (bearings, seals, posi, gears) and set up correctly. Some will reuse gears with new bearings, but you run the risk of noisy gears due to the old wear pattern.

 

Ever solve this?... The BW9 rear in my 88 also makes noise above about 20 mph...ran it on jack stands and it was pretty clear that it was the rear... Not the axles, but from the front of the rear end housing... I figure I have a total tear apart coming....

 

To close this up... Reached out to OP... It was bad pinion bearings... I changed mine too and solved most of the noise... But need to do a proper pinion set up now

 

I´m the same.

Tomorow I'll get a impact gun in order to start disassemblie with the pinion nut.

 

Good luck.... I actually broke a socket trying to get mine off... But I did get it eventually with an impact gun...