i have a 1991 trans am gta tpi with a 350 and a 700r4 transmission. my friend is selling 3:73 gears out of his 1996 firebird formula. will his gears fit in my car ok?

 

What type of rear end do you have?

 

Later GTA likely means you have a 9-bolt, thus no, they won't work. Count the cover bolts to confirm. - If you do have a 10-bolt, then the next question is, is it for sure a 3 series carrier so that they will fit.

 

I didnt think the 9 bolt made it to 91 did it? IIRC wasnt it 87-90, with 90 being the only year with PBR brakes? Anyways its necissary to know what rear you have,(count the cover bolts) and to know what gears you have currently.

 

Yep. GTA, some of your questions can be answered in the following link:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

A 1991 should have a 10-bolt, and a GTA should have come with 3.23 gears on a 3-series carrier.

If your friend's 3.73's are also for a 3-series carrier, then yes they will fit. However, its not a bolt-in swap. The gears need to be installed by a professional with special tools to set up the spacing and the backlash. Otherwise the rear end will whine and howl, and possibly break on launch.

Don't forget you will also need to swap the plastic speedo gears in the tailshaft of the transmission so your speedometer will read properly.

 

if you are paying someone to swap the gears, i wouldn't trust used gears. it'd be worth the money to just buy new. it's not like they cost all that much. plus your wear pattern is going to be different than what it was in his rear end. and that could cause problems, ie noise, breakage.

 

^ right on about used gears. Once they've run and established a wear pattern, you need to maintain that pattern very closely or they'll make noise which equates into them not lasting long.

Not sure what year the 9-bolt died, but my 89' vert, which has an '88 production date (due to being shipped out by GM to become a vert), was a 9-bolt with the PBR brakes.