2500rpm at 80mph actually almost seems lower than stock. 3.55s with stock 245/75/16 I would run nearly 2700 at 80mph.

 

Thats strange.. If my speedo is off wouldnt my rpms drop after adjusting it? Sounds like one of us has something funky going on

 

Got a GPS on your smart phone? See what IT thinks your speed is, compared to what your speedo thinks.

 

Not a bad idea! Im gonna be bringing my truck in for service tonight.. So I will program my computer for 33" tires before I leave and see if that corrects my issue. at least that will be one less issue to deal with

 

Anyone have an idea of what sort of difference I will see jumping from 3.55s to 4.10? 300 rpms or so? It would be nice if i could still cruise between 70-80 without my engine screming at me..

 

Probably less. There are charts online that will tell you.

 

just did the math, its 2000rpm at 70mph in OD with 4.10 gears and 33" tires.. and 2300 at 80mph..

 

at 80, im at about 2400 with 4:56 and 35's which is pretty good

 

I know there is a calculator on the pit bull tire web site if you know most of the information you can get the blanks filled in there

 

When playing with gear calculators, measure your tires. If I remember correctly my daughters 33" BFGs only measure 31 9/16" tall. She has 4.56s, there's no tach but we wouldn't want to run 80 mph with that set up. Works good where we live though.