Positraction additive - GM or not?

I'm planning to refill my diff very soon, and spoke to a guy at the garage where i bought my vette from, about supplying some GM LSD additive. They don't sell the actual stuff, but he reckons the stuff they do sell (a ready mixed oil that you just fill up with) would be fine.
I guess what I'm after from you guys is a second opinion. Sorry, I don't know the actual make or type of oil that he's offering, other than that it's obviously some type of general "one size fits all" LSD oil. What would people recommend? Are the vette diffs that different to any other Limited Slip Diff, and would i therefore be wise to hold out for the correct type of gunk to put in? Or, has anyone had trouble free running with any other type of oil?
Cheers folks

only cost $4.50 from the dealer. not worth the chance. Though the other stuff may be fine. When i changed mine I didn't even consider using anything else but the GM posi fluid additive.

Hey Garry,

Yeah, it's not really the cost that worries me, as i know the proper stuff is pretty cheap - my problem may be getting hold of it in the first place! I admit i haven't looked into it that deeply yet, but i wonder if UK GM (Vauxhall) dealers would carry it. I can't think of many british GM cars that would use an LSD - they're all a bit weedy! Still, I'll give my local Vauxhall dealer a ring today and see if they don't say "a corvette?! get yourself a sensible car mate!"
Do you have a part/product number for the stuff, garry, so i could check if i'm ordering the exact same stuff?

Cheers

Thanks for taking the time to have a look at the part no.....

Just phoned my local Vauxhall dealer, and they do a limited slip diff additive, which the guy reckons they use in the workshop. I imagine that means its a GM product, maybe even the same stuffas what you guys use. However, the part no. you found must be US only, as he couldn't bring it up on his computer with that number.
How much do you put in with the oil? I've read "one 4 oz. bottle" and "one, preferably two bottles" in other threads..

Apparently the bottle i'm talking about is 500 millilitres, which is closer to 18 oz.

Cheers

You can get it from Ecklers, add it to your order of other things. Thats what I did. Went in for a $4 part and came out with $159 of other parts that I couldn't live without. (ecklers.com if you don't have a catalog)

thanks guys..
Yeah, got signed up for the eckler's catalogue not long after i bought my vette. Not used them yet, but the catalogue makes a really good read in itself!

Picked up the GM UK diff additive today, but one question still remains... how much to use?

Having said the other day that it was a 500 ml bottle, it turns out to be 50 ml. I have an old chilton's manual that came with the car, that runs up to '79. They say 4 fl oz. (about 110ml) But i know GM changed the diff carrier for my year, 1980. Does this mean the capacity is any different, or should i stick with 4 oz. (and get another bottle!) Any of you 1980+ guys and girls have any advice to share?

Thanks

Hi Theo ,, I always add two bottles of the additive .

Geo

Hi Theo , I checked the bottles out and they are 4 oz. each . All differential rebuilds I do I add the two bottles . I really do not know much about some of the other after market additives ,and so I really cannot comment on them . The breakaway point on the stock clutches is rather on the stiff side . That is the reason I install the extra additive , it has no detrimental effect to the operation of the clutches .

cheers

Geo