Thread: Gear ratio adjustments

So I'm using a stock L67 file as the basis for my top swap. I thought I did a mass copy of all tranny tables (to include the gear ratio tables) from one of my L36 files to make sure I didn't have any tranny problems. After a couple drives the tranny started banging in to gear and I got a code for an incorrect gear ratio.

My Impala has a 3.05 FDR. Can anyone (Trannyman maybe?) confirm if these three values are all I need to change and that they're correct for a 3.05 FDR?

Calculated Pulses Per Revolution: 25
Pulses Per Mile: 23310
Drive Sprocket Ratio: 1

Those are the values from my stock file, but I still seem to get that incorrect gear ratio code when used in a L67 file.

Originally Posted by QwikGT

i thought all the L36's have 3.29's?

No. Civy Impala L36s have 3.05s. The police L36s have 3.29s.

What tuner are you using? As much as this doesnt make sense, you cant simply copy tables from your stock file to a supercharged file that was intended for 2.93s. I know you probably have copied all of the numbers correctly but there is more to it than that and I am yet to see it work. Here is where a little math comes into play, but it depends what you use to tune with. If you are using HPT I can help out, if using PT then sorry I cant be of much help as it does things a little differently.

DHP PT. Unfortunate I guess. I'll go ask around at the Powrtuner forums to see what happens. Thanks for the input, Trannyman.

Whelp, by looking at some math suggested for going from 2.93 to 3.69, I think I've come to the right answer.

I copied the sprocket ratio (1) and pulses per mile (23310) from my factory file. Then, I used the following math.

2.93/3.05 = .960656
1/0.960656 = 1.04095535

So I used the PT to increase the value by using the percent tool and putting in 104.095535% on the 22.29 stock L67 PPR. That gave me 23.2 PPR. I guess this will work...

Crossing my fingers, but the settings I listed in my last post seem to work.