Thread: How to program 3.29's from 2.93 with HPT

I had contacted Dave at TripleEdgePerformance on one of the other forums for his assistance in gear ratio changing. When Intense rebuilt my trans they recommended a different tooth count reluctor wheel (VSS) and a speedo recalibrator. Unfortunately as you tune etc the pcm is seeing the incorrect speed. This always bothered me and I noticed a few people doing it w/o the spoofs.

The below quotes are great info for anyone considering a gear change that has an HPT or can have the programming done.

Dave, I've heard alot about you and talked with many guys. Quick one for you hopefully. Car is a 97 Bonneville, may as well be a 99, I swapped the harness and pcm last week. Do you have the parameters for 3.29 gears with HPT? I have a couple different ones and am looking for the definitive sure thing. Trans was updated by Intense when done the first time around. Basically went with one of everything.

thanks
Bill

Hi Bill, since you have HPT I am going to give the easiest sure-fire way that I use for 3.29s in place of 2.93s. First off make sure you have 100% STOCK 2.93 tables and numbers for everything trans related. Once that is verified go into the Speedo folder in the editor. You will see a handful of numbers but there is only ONE that you need to change and it works perfect every time. On the top of this menu there is "Tire size" and "Gear Ratio" You will need to re-enter the existing tire size but instead of 3.29 ratio that it has stock replace it with "3.69" . Leave the "Auto calculate" feature turned ON. click commit change and that is it! Its that simple. Many people calculate numbers are import numbers from 3.29 geared cars and it rarely works, dont ask why it just doesnt. You will know the method I gave you works because you will not recieve an incorrect gear ratio code and also in the scanner pull up Current Gear Ratio in the PID list. In 3rd gear it should read 1:1 and must be within a few hundredths or it will throw the code. So just change 3.29 to 3.69 and you are set. And just so you arent confused about why it already says 3.29 from the factory that is because the differential ratio is a 3.29. There is also a parameter for sprocket ratio and it will be 1.121 which after some math gives you the 2.93 overall ratio. Changing this to 1.00 does NOT fix the problem, just leave it as is and it will work fine. I hope this helps you out

Easy

When you do the above post, it's all automatically adjusted.

You don't want a final drive. That's considered the differential. You want different drive/driven gears.

That is because the only HD diff ratio is 3.29. It's all in the drive/driven gears. For links on all this, please search on my name and "trans info".

Basics are the HD trans comes with 37/33 drive/driven aka 1:1.121 combined with 3.29's this works out to 2.93 overall ratio.
Since the sprockets always count 70 teeth total, drive chains are always the same length and the splines are always the same. You can mix and match, to get a 3.29 ratio, you put drive/driven of 35/35 from an NA/not HD trans, multiply 1:1 by 3.29 diff and you have 3.29 overall.

I switched from my factory 3.29 to 2.93 ratio.
Unfortunately, I'm working with a majorly unmapped bin file in HPT with my '04 CompG.
Under Speedo tire size and gear ratio were already blank with Final Drive Ratio: Drive Sprocket Ratio reading 1.0.
Now, I've done some discussion with other tuners and we think that changing my Drive Sprocket Ratio to .870 should get me very close to 1:1 in 3rd.
I'm going to quick flash now and test this.