Ive got 33"s on my truck and with my gps speedo ap on my phone says my speedo is off roughly 6ish mph. Basically at 55 I'm doing 2500 rpm (c6 auto) and that's what I go by. I've seen lmc has a handful of speedo gears and I don't know which gear I should get once I find where and what gear I currently have. Anyone know where to locate the gear at and how much of a job it is to change out?

 

2WD it's in the transmission tailshaft, 4WD it's in the transfer case.
Remove the one bolt that holds the speedometer cable in and pull the cable out. The speedo driven gear is on the end, held on by a clip that you can pop off.
On a C6, the driving gear is part of the tailshaft and can't be changed. I "think" on 4WD the driving gear slides on and is replaceable.

 

The drive gears are all the same. The pitch of the teeth decide the speed. They should have a chart if they sell them.

 

Ok thanks when I get time I'll tear into it