killagt

iTrader: (3)

I know my GPS is MPH is right, cause I test it on many car and it show exactly like my edometer show, but on my camaro ( i just bought it, and I dont know any history about it ), when I travel 45mph my gps show 50mph, 65mph and my gps show 70mph. any one have any ideal ? thanks

bobbyd

iTrader: (10)

does it have aftermarket gauges? example white ones? or do you know if it has bigger gears?

wssix99

iTrader: (5)

The GPS is only correct on speed when you are traveling down a straight road. Even if you aren't, it will still be close to actual.

slvr98camaro

iTrader: (1)

what size tires does it have?

there is really only 3 main causes

- different size tires
- different rear end gears
- speedo not calibrated correctly

T.A.WS6

mine does the same thing too but i gave up already!

The Vex

mine does the same, except it reads 25% off... 20 is 25, 40 is 50, 60 is 75, 80 it 100, etc. outside of making me brush up my math skills, the odometer reading is lower than it should be also. for every mile i travel, it only registers as .8 miles on the odo. something to check/think about.

tripps

iTrader: (7)

+1, these should be the only causes for an incorrect speedo.