I recently put new tires on my truck (285 75 16). I was wandering do you have to readjust where the tranny shifts for it to run better with the new tire size? I know that the speedometer is around 5 mph off. Is this something i can do or does a dealer have to do it. Thanks

 

you can do it if you want to dish out around 399 and get a hypertech programmer. that could be worth it so you get more power also. other wise the dealer has to do it.

 

what kind of advantages would i get from the programer. Do you know what a dealer might charge? Thanks

 

You don't need to change any shift points...not with that small of a change. The speedometer can be adjusted though. I dunno what a dealer would charge to do it though.

 

ok

 

I check my speedo every chance I get. With most construction sights for hiways they throw up a radar gun and a display to see how fast your going. Its a rought check but if you are within 5(in most states) of the radar gun display and your speedo your ok. Check your local TV station for road construction. It helps...Cheep way to find out...Just my $0.02

 

I am in the same boat.
Today I ask my friend to drive in front on me and signal me when spedo hits 60 mph.
My speed was 50 mph and his was 60 mph. So my speedo is about 20 % off.

I will be calling dealer to find out how much. Also I guess my MPG was calculated wrong. So I can probably say I get 12-13 MPH now.