Well i was racing my buddy yesterday and i something happened that never did before with my car. It got a rebuild 700r4 vette servo and a 2500 stall(not sure the brand it was rebuilt before i bought it. Only 12k miles on it)Its got a huge haynes trans cooler on it as well. Are has 2.77gears behind a 9 bolt.It also has yokohoma yk420 tires with only 5k miles on them. Well we lined up and i reved the stall up to about 1600rpm and hit it. THe car spun like hell but the tach went into the red line and i let off right away. GOt back in the car about 30 minutes later and same thing but it shifted at 5600rpm right at the red line. If im goin from normal role and punch it it shifts right in the middle of the yellow. Trans doesnt seem to slip but i dont know if thats what this is. Is it jsut my tires spinning i dont know? Any ideas?

 

If the car is in drive when you punch it I believe the car will shift at 5200 from a dead stop. If your tires are spinning then the tach will shoot up until you hook the tires and put a load on it. Does that help? Sorry if it doesnt answer your question(s).

 

Use a datalogger or get an aftermarket tach to see if your tach is actually reading correctly.

I found out that the tach in my GTA is waaaay lazy when approaching redline when I was datalogging. I've always noticed it because if I tried to shift at 5200RPM, I'd have to let off the gas a little bit to let it shift, then get back on it. That makes me think that the governer in my trans is set to shift at 5500RPM in drive [mine is also rebuilt].

Well, with the datalogger running I did another run and shifted at 5200. The datalogger told me I spun the motor to 5950RPM!

Way past the efficency for TPI and way too hard on a 160k mile bottom end. No wonder I couldn't get this car to run better thne a 14.85 at the track.

 

Hmmmm....I checked mine the other day and it shifts at 4500 instead of 5200. I will have to recheck it again. Where do you get a datalogger?