Correcting speedometer?

[arlon]

Did the update for the tire size and now at highway speed the speedometer is 2-3mph faster than the GPS. Also did the firmer shift upgrade and it now clunks going into reverse, can't tell any difference going forward. If my mileage takes a nose dive as I'm now suspecting, I'll be one unhappy, broke but smarter van owner. I think I just got a very expensive single car ODB II reader.)-:}

[97CargoCrawler]

Well that's a bummer. Mine did nothing but good things for me, but I have 31's and the speedo and shift points were way off. Which model did you buy?

[arlon]

I got the JET 15015 (google it).. Maybe if I do more to the van in the future it will have some effect. Might also do something if I did the premium fuel tune but I really don't want to pay the price for premium.

[MountainManJoe]

Are you able to undo the changes you made, and return the PCM to factory config?

[arlon]

Very easy to undo it all. I will be playing with it a little just to see what I can come up with.

[LiftedAWDAstro]

How has the JET programmer worked overall? I will need to correct for the 4.10 gear change as I am not going to larger tires any time soon.