VSS buffer programming.

[56pan]

Can anyone point me in the right direction on programming the vehicle speed sensor buffer on a '93 C2500 6.5 diesel? Years ago, when I put the bigger tires on, I found the info here on how to change the jumper links on the VSS buffer to keep the speedometer accurate with the bigger tire diameter. I'm likely going back to the stock tire size now and can't find that info. Any help would be appreciated and thanks for your time.

[phantom309]

http://www.tbichips.com/drac/

[56pan]

:) Exactly what I needed Phantom. Thanks very much for your time and help.

Garrett

[trbankii]

Sweet! I didn’t even know that was an option.

[56pan]

I thought I'd add one thing here. The original article I read on this issue, (and I believe it was here on the diesel page), differed slightly. I think this is important, myself. That article said to mark the bottom of the tire at the sidewall, with the tire on the truck. Then an adjacent mark on the ground. Roll the truck until the mark on the sidewall was down again. Measure the distance between the two marks for the computation. This way, the flat spot is accounted for, and there's no inaccuracy in the rolling diameter of the tire installed on the truck. After I did everything, I checked the speedometer with a stopwatch and mileposts at 60 mph on the cruise control. It was dead on. Years later, checked it with my GPS and it is on the money.

[john8662]

Dipped modules can be had here as well as calibrated for your combination:

www.uniquediesel.com/drac

[trbankii]

This way, the flat spot is accounted for, and there's no inaccuracy in the rolling diameter of the tire installed on the truck.

I wonder how much difference that makes? As you drive, the tire is going to heat up and the circumference will increase. This may be why it was recommended to take the tire off the vehicle to measure. As an experiment, it would be interesting to see how much it varies measuring it under different conditions - on and off the truck as well as cold and after half an hour of driving.

[trbankii]

Dipped modules can be had here as well as calibrated for your combination:

www.uniquediesel.com/drac

For $100, I think I’ll solder in some DIP switches myself.

[56pan]

I wonder how much difference that makes? As you drive, the tire is going to heat up and the circumference will increase. This may be why it was recommended to take the tire off the vehicle to measure. As an experiment, it would be interesting to see how much it varies measuring it under different conditions - on and off the truck as well as cold and after half an hour of driving.

Yes, but if that were the case, my speedometer would not have been dead on accurate.