changing rear end ratio from 3.08 to 3.42??

pitts12driver · July 18, 2016

I have a 2015 Silverado LTZ Z71 4WD with a 5.3L engine. Unfortunately it came with the 3.08. I'd like to change it to the 3.42 (I've figured out that 3.73 is WAY too much work).

1. Does anyone have the part numbers for the ring/pinion for the 3.42?

2. How hard is it to accomplish the swap (assuming a lift, full shop, and reasonably capable people)?

TJay74 · July 18, 2016

Swap isn't hard, part you wont be able to do is to change the ratio in the ECM/TCM. Dealer cant do that, so the only option you will have is to have the truck custom tuned. So if you are ok with doing the install then you need to be ok with programming the computer and taking a chance on voiding your warranty if you ever have any issues with the powertrain. Once GM sees a flashed calibration they are going to use it as an out to void the powertrain warranty if they can.

SILVER SLED · July 18, 2016

The dealer can reprogram the ecm/tcm for the change as long as its a factory offered gear ratio. They would have to call and get a program number and GM can change info in the "system" in case it had to come in for service.