Engine/Transmission (1998.5 - 2002) Strange gear in rearend

[LLiddell]

I have a 99 auto with Power Lock rear end. I opened it up to install a MagHytec cover and when looking at my setup I noticed a toothed gear running on the outside of the ring gear. Does anyone know what this is? I don't think it has anything to do with the drive train. Timing for something?

 

[Billy Diesel]

ABS tone ring.

 

[RustyJC]

It provides the signal to the speed sensor which, via the PCM, provides your speedometer reading.



Rusty

 

[LLiddell]

Thanks for the quick replys. It has to be one of the two and right now I don't need the exacts. Thanks again.

 

[RustyJC]

Originally posted by LLiddell

It has to be one of the two.....

It's both! The rear wheel speed signal is used for both the speedometer and ABS functions. That's why, if the sensor goes bad, the speedometer quits working and the ABS light comes on.



Rusty

 

[LLiddell]

Thankyou Rusty. I think I remember reading that the 99 is the only year with this set up. Also, if the sensor is reading the ring in the rear end for the speedo, does it read true if I make a tire change?

 

[RustyJC]

Originally posted by LLiddell

Thankyou Rusty. I think I remember reading that the 99 is the only year with this set up. Also, if the sensor is reading the ring in the rear end for the speedo, does it read true if I make a tire change?

My 2002 has it as well.



No, a taller tire means fewer ring gear (and, therefore, phonic wheel) revolutions per mile. If you have the "magic box", the PCM can be recalibrated for the new revolutions per mile figure for the taller tires, within a limited range.



Rusty