99redtrans

iTrader: (1)

im tryin to figure out what kinda 10 bolt rear end i have on my 99 trans am...do i have a 7.5 or a 8.5? its automatic with 3.23 gear.

Thanks

Valkyn

iTrader: (8)

All the 3rd and 4th gen Fbodys came with 7.5" 10 bolts.

99redtrans

iTrader: (1)

thanks

1 FMF

iTrader: (1)

i believe it's technically 7.625 (or 7-5/8) but everyone refers to it as a 7.5" ring gear size. wanna say when you look at gear sets you'll see advertised either 7.5 or 7.625 and either I think will work. you also want to verify the "series" carrier you have, and I want to say you have a series 3 so account for that when buying a new gear set or differential- make sure the gears are for the right series carrier.
Any axle with ratio of 3.08 or lower (down to 2.73 like in the automatics) was a series 2 carrier. Ratios of 3.23 (and 3.42 in the manual transmission cars) and higher were series 3 carriers.

https://ls1tech.com/forums/gears-axl...r-end-faq.html