The next revelation on my 95 Z28 has been that when I do a tight turn in either direction, there's a kind of wailing frictionish sound off the back end.
I'm wondering if it's the plates etc on the limited slip diff.
If so, can I drain, flush and refill diff and restore it. What flushing agent should I use btw.
Any help will be appreciated.

 

Maybe it didn't get posi-lube last change,I'd just drain it out and put the right stuff back in if you're not sure.
If that doesn't quiet it down it may be needing new clutches.

 

Somewhere I saw a post saying to clean diff with brake cleaner after draining.
Can't find post but keep thinking this might be a dodgy thing to do.
I have new oil and treatment plus new gasket ready.
Just need one last bit of knowledge about the brake cleaner thing before doing the job.

 

maybe use it to clean parts when rebuilding but have not heard of guys doing it when changing fluid.

 

Drained diff cleaned out with rags, let drain for a day too.
New gasket on cover, fill with new synthetic plus LSD goop, drive.
Sound is gone, all as should be and LSD works just fine.

 

This was common with GM LSD even when the cars was much newer even in rare cases still under warranty. I would see at least a couple noisy LSD a month at the dealership. In just about every case new standard fluid and GM LSD additive fixed it up. Your Synthetic was just a bonus for the rear. Most of the time when something goes wrong with the rear besides that the car shows up on a tow truck.