I have an '02 2500 diesel pickup that I want to change the rear gears in. I've been told that I would have to have the computer re-programmed or change the speedo gear for the speedometer to read correctly. Is this true, and if so, what would be the easiest way to go?

Starting in '98 speedo drive gears were no longer used, the ABS sensor on the rear end gives a speed signal so a computer flash with a factory DRB or electronic adapter (tuner) is the only way to change the calibration.

I believe you won't have to change anything when changing the gears. I went from 4.11 to 3.73 on my 03 and made no change to computer. Speedo is spot on.

Lucky you. It was off before, then.
3.73s and 4.10s are 9 or 10% different.

On my 1993 suburban I was tired of the speedometer always reading fast. I replaced 247-75-16 tires with 265-75-16s and that changed the speedometer to almost exactly dead on.

It is nicer to be able to correct things with a change to the software, though.

R.

like what was said above... The speed is a factor of tire size and axle RPM's from the ABS in the rear axle. So I don't believe changing the rear ratio would change the speedo. The speed sensor ring Diameter is the same, no matter which ring gear is used. Changing the tire size would. Not sure how GM does it but, a 93 suburban is not a 02 03 Dodge.

Okay, I had to step back and think.....You're right, changing only the gear ratio won't change the speedometer, but changing the tire size no matter what the gear ratio is, will.

It's true, I'm not up on newer trucks.

R.

Got the truck out of the shop today after the gear change. Speedo is spot on. Truck feels just as peppy from a dead stop as it ever did. I swear, every time I get behind the wheel, I love this truck more and more!