Rear diff chatter
 

Got most of my truck debugged, but can't seem to be able to get the posi to stop chattering. I had originally put in Amsoil and added 2 of their posi additives but the chatter was still there. Today I dumped that out and replaced it with GL-5 petroleum based 80W-90 and a bottle of GM limited slip additive. Chatter is still there. It's especially noticeable after a long steady drive.
Any secrets to get this thing to quiet down?

Re: Rear diff chatter
 

Have you tried doing tight figure 8's in a parking lot? That will distribute the oil through the plates and hopefully break them loose.

I've never seen one that wouldn't smooth out after doing that and using new fluid. I've got a Moroso Brute Strength in my Camaro with the heavy duty preload springs and it works smooth as glass.

Re: Rear diff chatter
 

I've put almost 100 miles on it this past week, including going around in circles. I decided to throw another bottle of additive in today, but may have to wait a week or so because we got some crap weather coming. Is it possible that the friction material has worn of the clutch plates? This was a low mileage truck, and I didn't even bother to take the posi apart because it was so clean inside.

Re: Rear diff chatter
 

i've got castrol 80-90 with the limited slip additive in it. No issues and have about 400 miles. What posi do you have?

Re: Rear diff chatter
 

Stock GM clutch type.

Re: Rear diff chatter
 

I know it's just not right but I use ford friction modifier cm-19546-a1 in my 70 chevelle 12 bolt with factory limited slip. A local speed shop recommended it. It stopped the chattering years ago and I love to launch the car hard.