gear ratio change wackiness?

cowboy5683 · August 8, 2005

Hello everyone...I hope someone can help me...I just got my gears changed on my '04 chevrolet silverado 2 wheel drive ext. cab to 4.56's from 3.73's and now the a.b.s. and brake light come on for no apparent reason!?!?....I was told it was a normal thing and would have no effect on my braking ...But i am still somewhat concerned ...So if anyone has the fix it would be greatly appreciated....Plus it is really annoying when it does come on...lol

Nick99Chevy · August 8, 2005

Hello everyone...I hope someone can help me...I just got my gears changed on my '04 chevrolet silverado 2 wheel drive ext. cab to 4.56's from 3.73's and now the a.b.s. and brake light come on for no apparent reason!?!?....I was told it was a normal thing and would have no effect on my braking ...But i am still somewhat concerned ...So if anyone has the fix it would be greatly appreciated....Plus it is really annoying when it does come on...lol

<{POST_SNAPBACK}>

Did you reprogram the computer for the new gears?

cowboy5683 · August 8, 2005

Yes sir i did...i used the hypertech power programmer III to do it and still the intermittent lights...what a pain in the ***....lol

pcrow · August 8, 2005

Had a similar problem. Went from 3.42/235's to 4.10/265's. Within 1.5 miles the lights would come on every time. Hypertech used to re-program for tires & gears. Turns out that the ABS is programmed for wheel speeds also, using inputs from tranny output, as well as both front rotors. If speedo is cal'd for new gears/tires, it can be far enough away from the ABS calibration (certian combinations) to make the ABS unit think the front & rear wheels were constantly spinning at different speeds. This throws the lights and disables the ABS system. Hypertech said that their handheld (and I assume others) cannot program the ABS, so the only solution was to keep reducing what you enter for tire diameter until it goes away. I ended up with a speedo error of about 3%.

A lot of people never see this, as they are going with very big tires, and Hypertech only allows programming up to 34". Therefore, they are programming low anyway.

I have also been told that a PCM swap/tune can also correct the ABS programming...something the handhelds apparently cannot.

cowboy5683 · August 9, 2005

wow...thanks a lot pcrow...but my hypertech has the ability tp program up to much larger tires than the 35's i have...maybe it's a newer version?...i don't know... but if i catch what yer saying right...you are saying to lower the tire diameter setting until the light no longer comes on?...if thats true i will find out in the morning...thanks again for all the great advice..

pcrow · August 9, 2005

No problem. The newer Hypertech's apparently do go above 34" if your's will.

Lowering the tire diameter is exactly what Hypertech recommended. As an example, with my BFG TA's (265/75), worked out to be an actual rolling diameter of 30.5" (1 rev in the driveway divided by 3.14159). If I plugged this number in, I get the lights every time. I kept reducing in the available 1/4" increments. At 29.25" I have never had the lights come on. If I go up even 1/4", I get them every time.

Good luck!