I have a 2006 H3 Hummer with some upgrades (Turbocharged, 4 inch Rancho lift Kit ,Rancho Suspension kit with reservoir, deep transmission pan,Electronic Ratio Adapter )
Now I upgraded the stock tire 265/75R 16 to LT 325/80x16 Pro Comp Xterrians on the stock rim
with this upgrade I am still worried because of the heavy weight and big size of the new tires might damage the differentials or the the transmissions due overheating or inappropriate gear shifting because this vehicle main use in extreme desert drag racing
My other question what is the maximum tire size I can put on the stock rim without significant loss of HP and torque and without damaging the auto parts
Your value input is needed
Thank you

 

I would be more concerned with wheel bearing failure and loss of power and milage. what is the diameter of your 325,s?

 

For drag racing you are fine as long as it's just a short burst of power. If the transmission light comes on, install an extra trans cooler. You can get them inexpensively at all sorts of places. One sign of tranny trouble is if you put on such a large tire that the torque converter doesn't lock up on the freeway. That gets transmission hot.

You don't lose HP or torque when you add tires, they are a function of engine output. As a rule, just compare the tires by comparing the radius. Divide them and you get the percentage decrease in torque at the wheel. Acceleration will be directly affected by that percentage.

The added power stresses drivelines up to the point the tires slip. The added traction lessens slip and so further stresses the driveline. That said, what typically takes out diffs is usually shock load due to wheel hop or really high stress low speed stuff where heat is building and lubrication is at a minimum. Doesn't sound like you have either and sand is forgiving. Not sure about H3's but other trucks usually break halfshafts before diffs.

Frank

 

My front diff went out with the facoty tires on a dirt road going 4 mph not in 4 wheel drive. I have 315/75/16 KM2's now and haven't had a problem

 

I don't think you'll be winning many drag races with that set up. Your tire size killed what you thought your turbo was adding. You'll be working on your driveline plenty, but I bet you'll have some fun.

Is the desert drag stuff on hard pack, or soft sand?

I do not know what the distance of an extreme desert drag race is, but we do plenty of serious sand drags up here.... they are short and sweet. You need a bunch of off the line jump, large diameter tires kill that, not to mention 5000# of truck?

Most of the diff issues happen in low lock, worse with the adventure series low ratio T Case. Add a little bounce to the front end under throttle and you have the recipe for failure.

 

That was a lubrication problem or that diff was not set up properly.

Frank

 

Dealer called a defect- under warranty