positraction lubrication

[Tom H.]

What oil and/or additives should I use in my 1972 corvette rear end? It is the original positraction unit.

[Joe L.]

Re: positraction lubrication

Tom-----

For a complete refill, I recommend using TWO 4 oz bottles of GM #1052358 limited slip differential additive and then filling to proper level with GM #1052271 posi lubricant. For just topping off, use the GM #1052271.

[Tom H.]

Re: positraction lubrication

Joe, thanks for the info. I will stop by my Chev dealer tomorrow and pick up both.

[Eric Fairclough]

Re: positraction lubrication

Tom , I used the G.M. gear oil and posi also in my 72. When i first got the car the rear end chattered alot all the time forward reverse i changed the gear oil and posi lube twice with off the shelf different brands. Then when i put in the G.M brand it totally quieted it down. I got mine from ecklers. That was a couple of yers ago and it is still silent. Eric

[Richard D.]

Re: positraction lubrication

Guys:

What do you think of using synthetic (like Mobil) gear lube with the additive?

I changed my trans fluid over to synthetic, and noticed better shifting, and was wondering if there were any drawbacks (propensity to cause leaking in gaskets and/or seals) to switching over for the rear.

It's an original posi, 3.70.

Thanks,

Rich

[bruce11495]

Re: positraction lubrication

I've ran synthetic in my rear end for a number of years and never had to use the additive. The rear end is quiet as a mouse...

[Clem Z.]

Re: positraction lubrication

i use amsoil rear gear oil in my posi without any additive and never change it in 100,000+ miles and the posi works perfect.

[Michael W.]

Re: positraction lubrication

I had 120,000 miles on my 3.36 diff when it was removed for inspection during a frame off. It ran it's whole life on GM oil plus additive. I wasted my money on the inspection and rebuild, it was perfect as is.

[Gary S.]

Re: positraction lubrication

I run Mobil 1 synthetic PLUS the GM brand of posi additive. Nice, quiet, and trouble free. Of course, I have only put 7000 miles on the car since the diff was serviced three years ago.
Gary

[Richard D.]

Re: positraction lubrication

Gary, that's what I intended to do.

Did you do yours as part of a rebuild, or just to change the fluid because it was due to be changed?

Is the recommended change interval at 36k miles?

Rich

[Gary S.]

Re: positraction lubrication

Both. When I had my 66 I used it as a flush and refill. On my 72, I swapped in some user friendly 3.36 gears and did a complete refill with both fluids as described.

Gary

[Richard D.]

Re: positraction lubrication

Thanks Gary, I will do as you did with the Mobil syn. and GM additive.

Quick Ques - I planned on using a suction hand pump to suck out the fluid, then after cleaning the pump and tubing thouroughly, using it to "inject" the fresh fluid back in to the fill recommendation. Is that how you did it when you serviced our 68?

Rich

[Gary S.]

exactly *NM*