First of all thanks for all the past help. Now for my current problem. I bought my '97 F-150 ext. cab, 4.6l with 265 75 R16 tires (factory was 255 70 R16) used last year. I added flowmasters and K&N filter. My speedometer has always read ~10% HIGH (65 mph when actually 60 mph and 88 when actually 80 mph). You would think it would read low due to the increase in size. I have recently installed a Superchips 1715 programmer. I called both HyperTech and Superchips directly. HyperTech said they didn't support the speedometer and tire size adjustments but Superchips said they did..........they didn't. I'll be contacting them Monday. I called my local dealership, they say to replace the instrument cluster ($400.00!), I don't think so. I called a local aftermarket store, they say they may can "calibrate" it. I have also been told I can change the gear size in the rear of the transmission, which drives the speedometer. I'm not sure on who to trust. Whats your advice? Thanks again.

 

have a 98 and need to recalibrate my speedo. On the 98 and 97 models, the tire size is not computer controlled even though the dumbass at ford told me to take it into the dealership for them to program my computer to have my speedo fixed. (another story) Anyway you should just have to switch out your VSS gear which is in the tranny. I haven't done it yet on mine because they don't don't majke the right size gear I need. (3.90 if anybody knows where I can get this gear please let me know) doesn't look very hard.