durty

iTrader: (3)

I might just pull the diff cover, just to make sure its not been geared, i know it runs tons better than my dads stock 99

Ferocity02

iTrader: (59)

Easier method would be to block the front tires, jack up the rear end, put the trans in neutral, and turn the driveshaft by hand and count the number of driveshaft turns required to turn the wheels one turn. That number is your gear ratio. And you wont have to buy new fluid and gasket. Unless you want to change the rear oil.

durty

iTrader: (3)

checked cruise rpms at 60mph(80mph) on the way home from work, cruises 2k rpm @ 80

Ferocity02

iTrader: (59)

Then according to my calculator you have 3.23 gears. Sounds like the tune was set for different tires and/or gears.

durty

iTrader: (3)

i gonna check the gear ratio tomorrow, gotta know for sure so i can get the tune right

durty

iTrader: (3)

RPO codes read GU6/3.42s, so 2000 rpm is actually 74.37mph, nothing other than an off tune cause the false MPH reading?

1FastBrick

iTrader: (17)

If the gear ratio is off it will usually throw a Check engine light and an ABS light. The front wheel speed and the trans ratio combined with rear gear ratio and rear tire size need to match within a specified range.

Most likely the tune has the wrong tire size and needs to be adjusted. Even with the correct tire size, it still may need a fine adjustment. With the correct tire size, Mine said I was doing about 85 when a GPS only showed 81. There is an option in the tuning software that will allow you to fine tune and correct for this.