4.88 gear question... How to calibrate the speedometer? (3 Viewers)

[linuxgod]

I know other manufactures dealer can usually change the REV's Per Mile usually up to a 315 tire size , anyone know if the dealer or Tech Steam is there any REV Per mile adjustment ?

My copy of techstream does not allow for that

 

[kcjaz]

So I know the speedo is based on wheel speed sensors and when I moved up to 285/70/R17 it displayed a higher speed relative to actual speed than with stock tires. It actually made the speedo dead nuts on compared to gps. But the odometer was now off by about the rev/mile ratio of the OEM to larger tire.

I thought the reason the stock speedo read hi was due to some Japanese law and JDM vehicles were calibrated this way but the odometer would need to be correct so I thought they used a transmission input/output sensor and calibrated that one without any bias.

I just got 4.88s installed and was expecting to have to do something to recalibrate the odometer but the odometer is not affected with the new gears so that must mean both speedo and OD are based of wheel speed and just must have different correction factors applied to the same wheel speed input.

The error is only 3.9% so it isn’t really a big deal to me but I’m curious if anyone has installed one of the correction devices. I think it may not be possible to fix both the speedo and OD if the same speed sensor input is used for both speedo and OD without getting into the ECU logic and changing something downstream of the wheel speed input.

 

[bloc]

I think it may not be possible to fix both the speedo and OD if the same speed sensor input is used for both speedo and OD without getting into the ECU logic and changing something downstream of the wheel speed input.

When I dug into this years ago that was my takeaway.