Ybnormal

I have several bottles of the old GM Posi rear end additive PN 1#1050428, I believe it was made with whale oil. Do you think this stuff is still good after all these years? I believe I bought it around late 70's.

Thanks.
Steve

jhopper408

I wouldn't use it. Just buy new.

2airtime2

I quit using the additives yrs ago and just use a synthetic gear oil rated for posi. Been using it in 1/2 and 3/4 ton p/u trucks with posi for yrs with no issues.


That stuff from the 70's might still be as good as new but that might not be very good compared to today's stuff???


Why wouldn't it still be good? It's already a few hundred thousand yrs old, what's a few more decades?

jhopper408

Lol. Yeah new additive couldn't cost that much.

jhopper408

And I bet todays oil is better!

Mod75

I have two bottles left, bought a dozen a long time ago.

3X2

It's a friction modifier. If you don't mind a little chattering when turning, don't use it. I personally don't use the stuff. Think about what it does- reduces friction in the posi plates. That equals heat. More heat = more slippage. More slippage = more wear. I prefer Mobil 1 75w-90 Delvac.

MCMLXIX

friction=heat
friction= wear
reduce friction=less heat, less wear

jhopper408

There's no reason to use old oil. Just purchase new!

3X2

You are misunderstanding its function. Without the additive, the plates stick/grab causing a chattering noise/feeling when turning. Adding the additive causes the plates to slide between themselves easier causing heat. Therefore heat causes wear. The tighter the posi plates are held against each other, the tighter the posi unit is. That is a good thing. What I mean by friction, in this case, is it increases the breakaway torque of the posi.

jhopper408

Oh okay. But when I took mine to the speed shop they just put the correct posi fluid in it. They didn't say a thing about a additive in. Maybe I just didn't know.

3X2

Some gear oils have the slip additive already in it.

MCMLXIX

The additive allows the posi to function as it was designed.
To smoothly slip and lock up and not bang and chatter.
A slightly less breakaway torque that operates smoothly will transmit more power to the ground.
Sand something dry and then wet sand it.
Witch one removed more material?

DaClown

I have an inconsistent noise in my 78 Pace Car. I siphoned the fluid out and added a bottle of GM Positraction lubricant and filled with Lucas Oil 89/90 Gear Oil. I'm sure it's a coincidence, but at 40 to 70 mph I let off the accelerator and the *** end noticeably slips right to left as if on ice. Whatup with that? Thanks

dmaxx3500

i'll take em if you don't use them,

jhopper408

I've had 5 corrvettes. 3 C3s And two C5 Zs
I've always changed the rear end fluids

jhopper408

And you've have to to change them every year period!

jhopper408

What happens the cluches are slipping from side to side which are giving that that performance. I had a 1966 Riviera and it did the same thing. Keep changing the fluids. And I guess a additive.

jhopper408

Sorry about the writing I'm on a I phone.

Tampa Jerry

DaClown: If your rear is feeling like it is moving after you let off the gas, check the shims and the bushings in your trailing arms. This is a classic symptom of the rear steering the car. Jerry