Im having some problems with my rear axle. Instead of fixing this one I figure this is a good opportunity to swap in one from a junk yard with 3.73 gears instead of the 3.55 gears I currently have. My question is will I have to reprogram the computer either with a programmer or let a dealer do it to compensate for the gear swap. What problems will it cause if I don't. The speedo being off don't bother me too much I just don't wanna kill my transmission or hurt anything else.

 

Being 3.73 is a factory optional gear, I don't expect you'll have major issues. Your engine and transmission will be turning more revolutions at any given speed. If you have cruise, I would expect that to work with the difference is it would think you're driving faster than you actually are. Because your speedometer would be off unless reprogrammed, so would your odometer (showing more miles than you've actually gone).
I don't know with the electronic speedometers and transmissions if it would cause issues with the transmission shiftpoints or not in relation to engine torque and speed.

Dealer could change the gear ratio in the computer and I believe some programmers can also.

That's about all I know on the subject. Last rearend I replaced was on a car with the gear drive speedometer, so just changed that in the tranny.

 

Changing to a 3.73 will present no issues. As far as changing the information stored in the PCM to reflect the change is a matter preforming the procedure using IDS Programmable Parameters feature. Your local dealer should be willing to do this for you for no more than what the standard diagnostic charge would run you.

 

Thanks for the replies. Those are the type of answers I was looking for.