speedo calibration

[DJM]

Does anyone know if you can recalibrate the speedo by yourself I know you can buy thing's like the Truespeed or some chips give you the option but the chips only go to 35's. Anyone know?

[mschn99]

he only way to recalibrate the PCM and ABS module for tire size is with a programmer or factory scan tool. The computer in the truck is only capable of compensating for so many revalutions per mile....if you need more info...let me know...

[fleastang]

My late 99 would not change with a programmer (has to be later models, typically those with a digital odometer) so I bought the Superlift device and it works fine. The speed signal comes from the sensor at the rear differential and ties in with the ABS function. This device just runs in series with the signal wire and allows you to change the input to make your speedo show the proper speed. I used a GPS to show true ground speed and adjusted accordingly. That works much better than mile markers or following another vehicle for adjustment.

[nss8425]

I went with the Jet Accu-Speed Speed Control Unit it installed easy and was alot cheaper than the Truespeed. The only real differnce between the two is the truespeed can be set for 2 tire sizes while the Accu-speed can only do one.