oversized tires & tranny - Diesel Forum

sethringer · 07-15-2003, 07:28 AM

Just installed my new 255/70/22.5 rims and tires on my 2003 F350 6.0 4x4. Looks great! Would like to know if any of ya'll know of a program that would recalibrate the tranny so that my speedometer would run true. thanks, seth

frobozz · 07-15-2003, 07:35 AM

Supposedly your dealer can reprogram the PCM for you (the main engine computer, which drives the speedo, not the tranny computer... because the speed sensor is on the rear axle). There are limits to what you can change it to, and some dealers balk at this or charge a lot of money for this even though it's just a matter of typing a number into a computer. See the 7.3 Upgrade and Aftermarkets archives for the horror stories...

Duncan

Redeemer · 07-16-2003, 02:13 AM

Superlift makes the truespeed calibrator small black box little over hundred dollars Im gonna get one for my truck running 40s.

sethringer · 07-20-2003, 02:48 PM

FORD COUDN'T/WOUDN'T REPROGRAM SAID THE TIRES WHERE TOO BIG (36" DIAMETER). WILL TRY THE SUPERLIFT BOX. THANKS GUYS, SETH

lad52 · 07-20-2003, 04:38 PM

The maximum tire diameter that the speedometer can be adjusted for in the computer (from what I understand) is 35".