In about a week I'll be lifting and getting bigger tires put on, need my speedo adjusted. Anyone know where I can take it or what to do...?

 

Handheld tuner will do it, plus wake the truck up.


SJ03

 

Why sweat it? Just determine the error and compensate. Mine is 4.3% off, when the speedometer says 76, I'm doing 80.

 

Doesn't the transmission sort of base the shift points on RPM and speed? If it's got inaccurate speed it'll have a poor shift pattern.

 

More likely load and rpm. I suspect 4.3% is a negligible difference in that context. With 265/70s, 80 mph was 2,020 rpm. With 285/70s, it's 1,980 rpm. Mine shifts fine and has chirped the tires on a 1-2 shift from time to time.