Which Differential Additive? Posi-or Limited

[like2drive]

Am getting ready to again change out the lubricant in the rear end of my '81 (automatic), but I'm not sure which to use: the Posi-traction or the Limited-Slip? I know to use the real GM stuff. Fact is , I bought some today at the local GM dealership. They gave me the Limited Slip stuff but I'd like to know for sure...(don't trust the kid at the dealership or my memory)
Incidentially, I was told this should be done every 15,000 miles.:cool

 

[FRANKD]

The service manual calles for a limited slip fluid, GM part # 1052271 or 1052272. Before filling with above lubricant, add 4 ounces GM part #1052358 lubricant additive.The manual says to change the fluid after the first 7500 miles and every 7500 miles after that when using vehicle to pull a trailer.

 

[Ken]

Posi-Traction and Limited Slip are basically the same thing, different manufacturers use different terminology when naming their units; Sure-Grip, and Traction-Lock are a couple of other terms to describe the same thing.

 

[like2drive]

Appreciate the response

:BOW :BOW Frank and Ken,
thanks for taking the time to respond. Yes, I eventually found the Limited-Slip recommendation in my glove compartment manual. ...which i put in today.
I don't know if the Positraction and Limited Slip additives are the same thing, but Positraction and Limited Slip differentials are not. I don't know which we have: Chilton/Hayes says its positraction; the manual calls it Limited Slip.
Anyway , thanks fellows. Jim