Hi there, dont know lot about whats inside my car, im trying to figure it all out. The tranny in my car was bought used before the car was sold to me, there is no sticker in the console (it was pealed off) and i cant find much more information on it. (dealer bought it at auction and had little information on it other then accidental history) Its a 89 GTA 350, w/posi and an alum driveshaft (is that stock?).

Anyway, on to the question. According to my calculations, my top speed is 300+kph. i know this because my guage went past the 220kph and kept going right on past the khp/mph sticker and right on past it. According to my tests at 4th gear every 1k rpm is 56kph. And at 250 (About) i was at just over 4.6k rpm and with an assumed limit of 6k (i dare not rev it past that) thats more then 300. In third gear at 5k rpm, im going around 130kph. Anyone know what gears i havE?

Im curious about this because one day i found a nice long flat strait highway as long as long can be, and just let it go. And to my surprise i went right past the limit of my speedo and kept on going. I belive my speedo is accurate. My buddies capri was driving along side me both going 50 and both are speedo's read the same (well within about 2kph, but thats expected, there both aging cars). (i thought my speedo was miss calibrated)

This confuses me because i can still break my tires loose on dry pavement even at half throttle with decent tires....but how could i have such i high top speed then? and smooth operation all around, something doesnt add up.

 

your rpm at 70 mph roughly equalls your gearing. just look at yuor rpm and make it a ratio, like 2700 rpm becomes 2:70 so it'd be safe bet to think you have 2:73 gears. sorry but you lost me with the metric stuff. i'm here in the states and we have yet to catch up with the rest of the world with out measurement system, or have yet to convert the rest of the world to ours.

 

Instead of trying to figure it out by driving, You could just get under the car, mark the driveshaft at a certain point, and mark the tire at a certain point, rotate the drive shaft and count how many times it goes around before the tire goes around once. That will tell you roughly what rearend gear you have. So if the drive shaft rotates about 3 1/2 times and the tire goes around once, then you probably have a 3.42:1 ratio. Let me know if I am unclear.

 

You could still have great top end and tire roasting ability with low gears 3.08s, 2.73s. Welcome to the world of a 5.7 TPI engine where low end torque is king!

 

k, great responses, thanks, Ill try both methods and compare.

 

pulling the cover and looking at the gear or the ration stamped on the gears is the only real 100% accurate way to know what you have.

 

I got 2.73s and i break them loose at 80

 

I have to agree with ede that pulling the cover is the only sure fire way to know, but if I had to take a stab at it, I'd say you probably have 3.23's if it's a ten bolt or 3.27's if it's a nine bolt rear. This is the stock gear ratio you usually see in the 5.7 cars with an automatic. 3.42's only came stock in the v6 and 5.0 G92 optioned cars. 3.45 for the nine bolt. You probably have a nine bolt in that year GTA unless someone's replaced the rear before.