well i work at a GM dealer and was wondering when i install my 4:10's in my car, could a Tech 2 or any other computer dealers use be able to re-calibrate my speedo?

if not i guess i'll need to talk to pcmforless or Madz28. What else could a computer tune do for my car with the mods in the sig. i have a Manual fan switch also

 

A custom tune on a nearly stock car is good for about 15HP.

 

but how does it acutally get 15hp? what variables in the computer cause it to make more power on a nearly stock car?

 

I am a GM technician at a dealership here in Lincoln, NE. No, you cannot flash the PCM with an updated calibration for the speedo as far as I know.

You will gain a few ponies, probably 10rwhp max out of a tune from a stock car. The extra ponies are coming from changing your fuel delivery at WOT. GM tends to richen things up a bit too much at WOT in order to try and avoid detonation. If you have a 160 thermostat in there like I see you do, you can lean the A/F mixture out a bit at WOT thus giving you a few extra horsepower.

 

i know you can reflash for diff. rear gears with tech 2. my old team leader at hargrave mceleney in iowa city ia did it to his truck. went from 3.42 to 4.10
the only problem is it has to be a populor gear. they will only do it for employees of gm dealers though. you have to call tech. assistance under tech 2 i beleve to get a custom flash

 

hmm, im gonna have to ask one of the mechanics. Cause i dont see why they wouldnt cause we have GMC trucks, and what if someone wants to replace their gears with another ratio, dealer would have to recalibrate the speedo for the customer also.

 

a gm tech can get different calibrations for gear ratios and tire sizes they can call techline and request a VCI #, but the gear ratio or tire size has to be an option availible on that vehicle from the factory

if you had a 3.42 gear and swapped to a 3.73 you would be fine if gm made that vehicle with a 3.73 option

i work as a gm service tech and have done this several times, the phone number to call is in SI, be sure to have the vin and all info for the vehicle, and dealer #

 

Well im gonna go from 3:42's to 4:10's

 

I guess with a VCI it is possible. We do tire size changes with VCI calibrations. It will usually cost $50 if I remember right.

 

whats a VCI? we do change truck tires, (upgrade GMC's from stock 17's to a 20inch or 22). Im not a tech at my place, but the techs will "hookup" other employees for next to nothing. But does the VCI change gear ratios?