NEED SOME INFO ON SPEEDO GEARS FOR MY 97 GT AND T45

I always understood that for the 96-98 model year cars with a VSS sensor the rear end gears are adjusted with a PCM tune. Or with an external electronic box such as Speedcal.

The changing of the speedo gears works for the older cars.

The speedometer appears to be mechanical on the 96-98 mustang, but it is actually driven by an electric motor instead of a mechanical cable arrangement like the older cars. Thus, you will need a speed calibrator instead of a swapping out the gear.

I put 3.73s in my 96 and swapped out the speedo gear and got it close. I think it is off by 4mph now.

I have 4.10's in my 98gt 5speed

guys at cjponyparts did the entire install and gear speedo correction....

EXCEPT
its not perfect, in fact its off.

I believe they used a 21 tooth ill have to check my receipt.

The faster I drive the more the MPH is off.

I got a great deal from cjpony parts ($535"i believe thats what i paid cant remember" including tax for frpp 4.10s speedo correct and labor, install kit, etc.) I didnt have the money, but if i did i would have probably gotten the ford racing speedcal (i think thats what its called)

anyway the guys at cjponyparts told me that going with anything higher than a 21tooth has led to failure. i think i remember them telling me they tried a higher teeth gear 23etc. and they were breaking.(in other cars)

dont quote me on that exact cause but im pretty sure thats what i remember ill have to check my receipt again to make sure the numbers are correct.

its not the worst thing in the world. On the highway i just stay with the flow and i also have a gps that shows an est mph display. I pretty much figure its in between the 2 readings i have. its kinda ghetto but its not the end of the world. Like i said the higher the mph the greater my speedo is off.