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69HuggrrrPT
04-18-2005, 06:21 AM
I am about to change my rear end oil, 4.56 12 bolt posi. I have Quaker state 75/90 full synthetic to put in. My question is would I still need GM posi additive?
It says on bottle....
"These thermally-stable products are recommended for vehicles with manual transmissions and conventional or limited-slip differentials, especially where extremely low-temperature shifting can be a problem.

Thanks

chicane67
04-18-2005, 10:03 AM
Well, you dont 'shift' a differential first of all....... a transmission oil is just for that (which what you really have) and unless you deal with freezing temperatures a fair amount of the time you drive the car, I would use a strait 140 weight oil. Something from Torco, Amsoil, Schaffer or LE, designed for use in differentials....

Honestly, to answer your question, it may depend on your posi. Some newer and tighter limited slips might want a little extra additive and some might not. I would drive it and not add it unless you get the 'tell tale signs' that it requires more additive.