Went to a 35x12.50 tire on 01 S-crew, now the speedo is off about 5 mph. Is their anything that can be done to correct the problem.

Thanx

 

Most speedos are off by 2 or 3 mph anyway. I believe Mike T. can make adjustments with a MicroTuner or a SuperChip.

There are also "black boxes" available on the Internet that you put in-line with your tranny's electronics to modify the speedo readings. Most I've seen are $100 or so.

If you don't have a chip, put the money towards that and get the added chip benefitts as well...

 

I installed and Electronic Ratio Adapter on my mustang. After a swapped in a 3.73 gear I was able to adjust to within 1%. I am sure it can be used on the F series too but you'd have to find a tech with wiring diagram to figure out which wire to splice to.

The company is Abbott Enterprises.

http://www.atrol.com