I have recently purchased my first of many Ford trucks. I have begun toying with it and have upgraded to a larger tire size. When I upgraded from stock to a 285/75 15, I lost a good chunk of my fuel mileage. I was reading on the Hypertech and found out that I can't change my tire size and gearing with this particular model. I was wondering if anyone knew of a programmer that would allow me to change the tire size and regain some fuel economy. Any suggestions would be appreciated.

 

All you have to do is buy a new vehicle speed sensor gear. Not sure what one you need, but it shouldn't be more than a few bucks. Also, your tires are at least a 16" rim....

 

15" was a typo. Is there a programmer that will recalibrate the new tire size? I was also hoping to get some performance upgrades as well as a change in shifting. The truck was used primarily for towing and has a gooseneck hitch so I would say the load was heavy. The transmission acts like it has been used for heavy towing.

 

On your truck, you will need to change the VSS gear. But, you can still get a power programmer. Your best bet would be to go with a XCalII tuned by Mike Troyer or an Edge Evolution chip which I have and love.

 

OK. I have been looking at the XCal 2 and seems to be the best for what I am looking for. Thanks for the help.

 

One more question! (at the risk of sounding dumb) How is the VSS going to help gain back fuel economy? I guess I am just not sure what the sensor does beside recalibrate my speedometer.

 

The larger tires are throwing off your spedometer, which is in turn causing you to miscalculate your gas mileage.

 

That makes alot of sense. Thanks for all the help.

 

Yes, exactly - the speedo being of also throws off the odometer and in automatic transmission models, the shift pints as well - so with the odo off, you can't calculate the fuel mileage accurately.

In the Ford F-series the ability to recalibrate the speedo via flashing the PCM starts with the 1999 model year.