14 to 15" wheel & tire change

[kimfish1]

In changing from stock 225/70r14 to 235/75r15, the diameter will increase 26.4 to 28.88", circumference from 82.9 to 90.7". What will I need to do to keep speedo accurate and not compromise the tranny (4R44E) automatic or the computer? The new wheels will set out 1" farther which is actually a bonus and clearance is not a problem. Thanks to anyone who can help.

 

[lil_Blue_Ford]

There are calculators in the tech pages for determining what exactly the effects of the change will be.

IMHO, the real thing to watch for would be what gears you have and what engine. My 88 BII I ran the stock tires (215/70/15) with 3.73 gears, a4ld trans and 2.9L motor. My 89 BII (which I sold, wish I would have kept it) had 235/75/15 tires, 3.73 gears, a4ld trans and 2.9L motor and was just fine with that setup (AFTER I did a much-needed tune-up, seems the previous owner did not believe that they needed maintenance very often - if ever - in the roughly 220,000 miles before I got it).

My 00 Ranger had 225/70/15 tires stock, 3.73 gears, 3.0L motor and a 5-speed stick, I swapped to 235/75/15 tires and when I checked the speedo, I found that it had actually corrected it (it read a little off from the factory).

My 95 F-150 had 235/75/15 tires stock, 3.08 gears, 4.9L motor and a 5-speed (and was a dog). I changed to 31x10.5x15 tires (and it was an even worse dog) then changed to 3.55 gears which corrected the speedo and gave me the power I wanted.