Axle swap- speedo correction?

[iamdrew]

I'm thinking about swapping the noisy 3.23 open rear end in my '07 Classic Crew Cab for a 3.73 locker like I had in my '04 EC.

 

I have found several low-mileage '06s and even a few '07s in salvage yards for around $1500.

 

Can the dealer reprogram the PCM to make the speedometer read correctly with the new axle ratio?

[95Sierra2500]

They should be able to. Just make sure that if you have a 4 wheel drive truck, you don't shift into 4 wheel drive until you have a 3.73 in your front differential as well, or you'll be experiencing some bad times and possibily need a new transfer case.

 

If you're 2 wheel drive, then do it and have fun!