Re: v6 speedometer help.
If you go from a 120 mph speedo to a 150 mph speedo it will read incorrectly. The MPH numbers will be moved to the left to squeeze in the extra 30+mph. The higher speedo you get, the higher it will be off.
1.) Fixes, get a tuner and tell it you have different rear end gears that will give you the proper ratio to set the speedo right.
Pros: Speedo reads correctly
Cons: You mileage on your odometer will not be correct because you are telling the computer you have different gears when you really don't.
2.) Take your car to a calibration place. I don't remember what they are called, but they can calibrate your speedo for the gauge you are using.
Pros: Speedo will read right, odometer will read right
Cons: No idea what the place that could do this would be called.
So, basically, those are your choices. Of course, you obviously also have the choice of leaving it as is and just knowing that when the speedo says you are going 70, you are really going 50...or whatever the shift ends up being.
"When I know more, I'll be forthcoming. Or I won't be forthcoming, and I'll be honestly deceptive." - Les Miles