I just replaced my stock 3.73 gears in my 2002 3.0 2wd and i took it out for a ride and the abs light came on and did not turn off. what causes this to happen?

 

How far did you alter the gears? because there is a PCM setting for gear ratio and its part of ABS speed sensor and a few other systems so if its out of range it can cause the other systems to act up. Its probably as simple as a reprogram but there is also a sensor on the reared tied to ABS so the sensor may have been damaged during the swap. Id check this things first.

 

I went from 3.73 to 4.10, when I first start it up it doesn't come on for a while and some trips that are 5-10 minutes the light doesn't come on at all

 

sounds like a configuration error in the PCM then when i went from auto to 5speed the speed sensor was different which is also part of the same system to control ABS function and so on at low speeds it was fine but when i would do interstate runs the % error was so bad it would trigger the light. So it sounds like only when you exceed the programmed allowable % error is when you get the problem so id find someone with a scan tool that can adjust the ratio in the PCM before you start throwing parts at it. Basically what its "seeing" is the speed sensor which is still calibrated for 3.73 is telling it one set of numbers but the abs sensor in the back is telling it different because it actually has 4.10 gears so the computer is fine at certain speeds but at others it sees a problem because the numbers between the two sensors are two far off. I hope that makes sense?

 

Thats what i figured it was, i know the PCM has a sensor at the top on the rear diff. the shop i went too has a Snap-On Solus system, will they be able to fix it?

 

Well your speedo will be off, when 40mph is shown you will be going 37mph, when 60mph is shown you will be going 55mph

Not sure on the 2002 but in 2001 they switched back to transmission speed sensor and not sure if the ABS speed sensors on the rear axle was still used, if it is then they could be reading different speeds.
The higher the speed the more the difference, so that could be part of the delay on the light coming on.

Or it could be the wheel ABS sensors are no longer matching the drive line speed sensors, again at higher speeds this would set the ABS light, not lower speeds.

 

I never had any ABS issues before or after gear changes on my '01. This includes 4.10 w/ 31's, 32's, 35's and 4.88 w/ 35's and 33's. Only "issues" were obvious speedo needle inaccuracies.


Was this an axle swap or was this a gear swap in your existing axle? Was the ABS tone ring re-installed onto the carrier during the gear swap? If it was an axle swap, was there a tone ring on the carrier? That's the only thing I can come up with as being the problem other than a damaged rear ABS sensor on the axle.