Is the 9 bolt a positraction diff or limited slip?

I did a nice burnout the other day but only one tire was smoking

My rear end is the factory BW 9 bolt with 3.27s--it was rebuilt a few years ago--maybe 10K miles on it.

No other issues.

Essentially the same thing.

JamesC

It'll only be a posi if you have a G80 RPO code. I think just about all the 3.27 geared 9 bolts do have posi but not all 9 bolts have posi. The 9 bolt was also offered with 2.77 gears. Not really a performance gear set that needs posi but some probably came with it.

Posi's don't last forever. They do wear out and need to be rebuilt or replaced. Since your diff was supposed to have been rebuilt, was the posi rebuilt as well?

Only difference is the BW 9 bolt has cone type posi's and 10 bolts use clutches. What exactly was done in the rebuild? the 9 bolt is a pretty hard thing to find parts for, so you must have paid a pretty penny to get it rebuilt, unless you did it yourself.

All 350 Formulas/GTA/Trans Ams were G80 3.27s
(only IROCs got the 2.77)

I will go over the recipets and see what was done
----------
previous owner rebuilt that (along with trans) Car runs great

5.7L IROC's have 3.27 in 1987. In 88 and 89, it was the G92 option while the 2.77 was standard equipment.

Some 305 IROC's with a manual transmission had an optional 3.45 9 bolt instead of a 3.08 10 bolt.

I meant to say IROCs have both the 2.77 and 3.27s
(2.77 was 88 and 89 with optional 3.27s)

Whereas Firebird 350s only had 3.27s for 350s period

i have a 87 formula 350 with the 3.27 limited slip 9 bolt, 4 wheel disk ... but my other 86 TA had 305tpi LB9, with 2.77 9 bolt with limited slip and 4 wheel disk.... hmmmm

and im pretty sure u cant rebuild the stock 9 bolt limited slip... they just replace it completly with a stock limited slip... which is weak as is. hate that they dont make aftermarket parts for the 9 bolt. so if he rebuilt your 9bolt he just made it a new stock 9 bolt which will die behind anything more than 300hp. still its stronger than a stock 10bolt

thought all the 10 bolt gears where... 2.73/3.23/3.42
thought all the 9 bolt gears where... 2.77/3.27

You could get 9 bolt 3.45 gears in 305 Formulas and IROC's with a t-5 and i have read somewhere on here that there were some 3.73 stock gears offered but i may have read that wrong.

3.70 was available over the counter from GM at one time but never offered in a production car.

3.73's were offered in L69 cars.

JamesC

3.73 are for the GM 10 bolt and are not available for the 9 bolt. I think they did offer the 3.73 in the 10 bolt from the factory but I'm not sure.

I'm sure.

JamesC