steve87ta

iTrader: (4)

I was wondering what is the posi additive and oil should go in an 86 T/A rear?

Thanks for any replies.

big gear head

If you have the 7.5 10 bolt with an Auburn then use 80W90 gear oil and 2 bottles of GM additive. If you have a 7.5 with the Governor Lock then just use 80W90 gear oil and no additive.

steve87ta

iTrader: (4)

Thanks, It is a 9 bolt with 2.73 gears and a "spin resistant diff" . The old fluid is sticky and clear so I think there was an additive in it.

big gear head

You will still need the 80W90 gear oil. I recommend using the GM additive, but others here say that the 9 bolt doesn't need it.

Gumby

Most everyone says 1 bottle of addtive for a posi/ls
but like for my 12bolt posi/ls I was told 1-1/2-2 since its larger/hold more oil, so it needs more addtive.



I got mine cheap from fleebay at Smittys but a GM dealer should have some too.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=270431285926

mooch1

hi , is 80-140 too thick?...for a posi 3-23 rear end(10 bolt 7.5)

big gear head

It's not too thick, but will increase drag a little bit. The 80W140 is usually used for towing applications.

Gumby

I dunno why, 80-90 is plenty and can be found anywhere cheap.

mooch1

ok ,thanks...i think that's what is in there ...just put it in this summer...so you say it won't damage anything with the 80-140?....i can always add a little 80-90 i guess...thanks.

Saabster

iTrader: (2)

I put in M1 75W-90 and it had LSD additive already in it. I can't speak to it's effectiveness though as I have an open diff.

mooch1

ok,,i don't remember why i put the 80w140 in ...i guess i can always drain it and put in the 80w90 in the spring...i was just worried with the thicker oil it would cause damage...i have a 3-23 auburn posi and i don't want to ruin it....thanks for all your help..

Gumby

It not gonna hurt anything but save your money next time, if real muscle cars of the 70s were fine on regular dino 80-90 and some addtive, why fall for techno hype to get you to spend 3 times as much........