so here is my question. i have a 91 RS tbi and i wanted to see if i can get a rough idea on my rear gear. heres the info i have. the trans i have is a Raptor 700R4 and when i am running at 65 mph the rpm is approximately 2700-2800. so if anyone knows how to figure out the approximate gear, please let me know.

right now it is a non locking rear but i am wanting to put a posi in eventually.

and if anyone knows anything about the Raptor transmissions, as far as quality and durability that would be good info also. i looked it up online and i think they are located in california

 

The TBI engine only came with 2.73's behind the 700r4, 3.08's with the 5spd. Best bet if you want to know for sure is to pull the cover and look.

 

i know about the gears for stock, but this thing for being a 305, which i suspect it is, just pulls way too hard for it being a stock gear.

 

As Drew mentioned, jerk the cover--the gear oil has probably never been changed anyway. The following FAQ provides info on the ring/pinion that should eliminate the mystery:

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

JamesC

 

and i konw the only true way to find out is to pull the cover, but im waiting till winter.

 

ok thanks ill see what else i can find out by using those links and pulling the cover.

 

You can look around online and find a calculator that will let you figure the gear ratio based on engine RPM, speed, tire diameter, and transmission gearing. But here's the thing, how accurate is your speedometer?, How accurate is your tachometer?, etc.

On the other hand, $20 worth of 75W-90 and a tube of RTV, and you'll know 110% accurately what gears you have. Like JamesC said, gear oil doesn't get changed a lot on these cars. If you've never done it, it probably needs it anyway.