When I bought the truck it was equiped with 27" tires.....but i upgraded to 29".

I wounder if I have totune the PCM for the new tiresize??

Can the tranny be damaged because of the different tire size?? Bacause I have reacently changen tranny!!

/Sverker

 

If you don't reprogram the pcm, your speedometer will be off. There are a few companies out there that make a programmer for about $300. Only increasing 2" isn't going to cause too much strain on your driveline, but it will of course cause some. Its not enough for you to really worry about.

 

ok!! Then I will sleep calm again!! Thank's!!

I not to worried about the speedometer, I can callibrate it with the GPS.
I have already done a checkup with the GPS when i changed into a white cluster för the
speedometer and had to replace the needles.
It is very accurate now maybe 1 mph wrong.
/Sverker

 

Yeah I had 28" tires and upgraded to like 29.5/30inch tires and I am only off by 1-1.5mph according to my garmin GPS. According to the online tire calculator it is a difference of 3% for me over the stock 235/70r15 tires i had. It shouldnt affect the drivetrain or transmission too much. The bigger the tires the biggest thing you will see is increased braking and acceleration times most likely since there is more rolling resistance/momentum. But yeah you should be good, just keep up on your fluid changes like you should normally and you will be good.