OK guys.... PLEASE HELP .... I have an 89 Trans Am GTA and my mechanic is pulling the 305 now and putting in the new L98 355 motor (300 hp)... He said it was a good idea to change the rear end out to a Posi Unit w/ 373 gears .. Heres my dilemma .... I NEED to know what rear end and gears came in my car from the factory??? Its an 89 TA GTA 305 5 speed car ... PLEASE FLOOD ME WITH INFO AND SITES .... I am on a short clock here ... Email is Gogzhero@aol.com if u need to email me.... Thanks yall ! Scott
Supreme Member
It should have come with a 9-bolt posi with 3.45 gears. Pull the cover and make sure BEFORE BUYING ANYTHING.
Putting 3.73s in that would be one helluvalot of maze, and very little cheese at the end. Probably near $500 by the time you're done just in parts, plus probably $2-300 labor, for a barely noticeable change. Besides, a 350 with TPI on it, isn't going to have the RPM capability to use that much gear, anyway; you'll end up with one of these cars that has this huge grunt off the line, and then it just runs out of breath (literally) after about a second or a second and a half in each gear. Like it'll feel like it'll pull stumps from a stop, but you'll barely be able to pass a Saturn on the freeway.
If you have the original gears, leave them alone, they're fine for what you're doing.
You have already found "the site". Can't give you any more to go to.
Putting 3.73s in that would be one helluvalot of maze, and very little cheese at the end. Probably near $500 by the time you're done just in parts, plus probably $2-300 labor, for a barely noticeable change. Besides, a 350 with TPI on it, isn't going to have the RPM capability to use that much gear, anyway; you'll end up with one of these cars that has this huge grunt off the line, and then it just runs out of breath (literally) after about a second or a second and a half in each gear. Like it'll feel like it'll pull stumps from a stop, but you'll barely be able to pass a Saturn on the freeway.
If you have the original gears, leave them alone, they're fine for what you're doing.
You have already found "the site". Can't give you any more to go to.
Thanks for the info man!