Hypertech and tires

[Ernie Italy]

Hi...
What happen if we set a 37" tires (or tyres) on programmer and use a 35 or stock size ?
Speedometer goes wrong or not ?
Thanks.

[HUM GOOD]

My question would be: When changing from stock to a larger tire, how does it effect the power - low end/top end. I'm sure it changes the ratios, but is it enough to effect power? If so, would just a change of tire size in the programmer fix the issue?

come on Taz - I know you got this one......

[tomp]

it affects power in two ways. One is the gear ratio is now taller, and the other is the sprung-rotational added weight of the larger tire. It also negatively affects brake performance as well.

Going to 35s does not hurt that much with stock gearing, but does affect it both ways above to a small degree.

Going to 37s is borderline where you might opt for 4.56:1 gears and, slotted rotors. Possibly a Programmer (a must for speedo).

[HUM GOOD]

Originally Posted by tomp

it affects power in two ways. One is the gear ratio is now taller, and the other is the sprung-rotational added weight of the larger tire. It also negatively affects brake performance as well.

Going to 35s does not hurt that much with stock gearing, but does affect it both ways above to a small degree.

Going to 37s is borderline where you might opt for 4.56:1 gears and, slotted rotors. Possibly a Programmer (a must for speedo).

I'm running 37s - what would be the cost of having 4.56:1 gears put in. I do feel like I'm pushing the truck a little to hard off the line.
My braking is not an issue....I always leave a large cushion between the lead vehicle and myself.

[tomp]

4.56 gears will put you right about where you should be, where the final drive ratio is really close to stock (with 37s). Actually, I feel the H2 should probably have had 4.56 gears from the factory.

Get the Yukon brand gears as they are rated very strong. Gears will run about 150 for front and 225 for rear. H2 GM diff is 9.5 for rear and IFS 9.25 for front.

You will need a rebuild kit for both front & rear. Depending on how many miles you currently have, will justify rather you need master rebuild kit or other - consult with gear manufacturer for their recommendation on the rebuild kit to use or just go all the way and get the master kit to reduce risk.

Might consider the front locker while you are in the front diff since it will be one prrice for labor for gears and locker.

Labor for both diffs should be right about $650

When you replace gears, put Dino fluid in for first 500 miles, drop fluid and switch to good synthetic.

[Ernie Italy]

....but....anyone have explain to me what happen if I use stock tire and program the Hypertech with 37"....