Posi Additive

[Joe C.]

Any thoughts on doubling up on the dose of posi additive (GM 1052358 equivalent) StaLube number SL2411 Equa Torque Limited Slip additive, from 4oz to 8oz?
The tube says "do not overtreat". I have done this before with good results.

[Donald L.]

Re: Posi Additive

I needed 2 doses of GM additive to quiet the posi on my C-1.

[John Liner]

Re: Posi Additive

When I change my 75 W/ 45,000 miles on it the Chevy Parts counter guy sold me 2 bottles of the additive with the lube. His remark was that they always used 2 bottles when they change fluids when the car had over 30,000 miles. This was several years ago. I have always done this since then on all my cars including my 95 SS. Have had no problems.

[Joe L.]

Re: Posi Additive

Joe-----

I always use TWO 4 oz bottles of the GM #1052358 additive.

[Joe C.]

Donald, John, Joe

Thanks for replying, all three. I generally have doubled up on the additive for a long time, now. I just found it strange to see the phrase "do not overtreat" on the 4 oz tube of StaLube Equa Torque Limited Slip additive.
Like a good Doctor, I try to "first, do no harm". I guess that StaLube has great confidence in their product, and/or the company is doing so well that they don't feel the need to peddle extra stuff (needed or not).
I'll continue my usual practice of doubling the dose, unless somebody convinces me that it is harmful.

Joe

[Scott Butville]

Re: Donald, John, Joe

Last year I had a discussion with a very helpful engineer at Auburn Gear on the subject of posi additives. A previous owner installed one of their posi units in my '64 and I had a problem with chatter after changing the ring and pinion. He said that I needed to use enough additive to stop the chatter and that some very tight clutch units need as many as three tubes to eliminate it. As more additive is used, the posi action lessens but otherwise there is no harm. I expect this also applies to the original GM supplied posi's as well.

[Roger Legge]

Re: Donald, John, Joe

The additive is a friction modifier, correct? It seems to me that if one used too much, your posi would not 'posi' like it should, meaning the clutches wouldn't 'clutch' and you'd end up with a semi-posi or something that acted like an open differential. One method for adding is to add one bottle, drive slowly in tight circles, both ways, listen for any chatter and add more additive until the chatter goes away. I'd rather have a slight amount of chatter than a lame posi.

Roger

[Duke W.]

Re: Donald, John, Joe

That's correct. It prevents the stick-slip friction that causes the vibration or noise (chatter) that we can experience and too much can reduce clutch holding torque, which effectively make the Postraction less "positive".

My recommendation is to start with just one bottle and fill the axle to a little below full. Then drive it. If you get chatter, add a half bottle (2 oz.) more. If not, fill to the full with more oil.

Duke