Determining gear ratios

[jakekooser]

Hi,

I want to figure out what gear ratios I have in the 915 in my '86 Carrera so that I can plug them into a formula that shows what gear you are in by RPM in my RaceCapture Pro data logger. I just saw another thread where the transaxle is out of the car with the procedure, what if it's still installed?

Is there a chart that I can look up the numbers on, and where would I find it for my car?

Thanks!

[Bill Verburg]

here are the tooth counts and individual ratios and overall ratios for a 915/68, 70,73 US 3.2 Carrera

cwp 8:31 3.875

35 32 29 26 30
11 18 23 26 38
3.1818 1.7778 1.2609 1.0000 0.7895
12.330 6.889 4.886 3.875 3.059

[Driven97]

here is the spreadsheet from instant-g's site. Pretty badass. Pick the 915-68-70-73 tab (matches Bill V's gearing above.) Just fix the redline and tire size to yours in the yellow boxes - the pre-entered ones are wonky.