Put a 3" Tough Country lift with some 31-32 tires in my 06 2wd Silverado Crew Cab do i really need to do gears? I think the guy at GM said they were 3.27 or something...will that 3" make a difference? Should i go with a Diablo Chip instead? Both? Thanks

 

The lift height really doesn't determine the need for gears or not. It is the tire size. (Even though they usually go hand in hand) With a 31" or even 32" tire you will not need to change the gears. That isn't that much bigger than stock. You can determine your exact gear by looking in the glove box. There is a white sticker in there with a whole bunch of codes on it. Look for the G codes (they are in alphabetical order). Here is a list of GM rear end codes:
Rear Axle Ratio
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)
HC4 -- AXLE REAR, 4.56 RATIO

 

Yeah if you go bigger than that, put some different ratio gears. If you keep what you got right now, ur ok then.

 

People tend to be a little jumpy on going to a taller gear set. Honestly you do not need it to swap unless you are going to 35" tires or do not have enough power. You are just wasting your time and money if you swap out the gears and you dont really need to. Your truck should have plenty to turn those tires.