Glad I found this forum!!

VRMMMM · January 27, 2002

I just picked up my Truck last week and it has a whooping 250 miles on it. .lol. time to start modding!! I will be towing a 4 horse trailer that weighs 11,000pounds. First thing is this thing need BIGGER tires!! Im thinking 285-75-16s I also want to do intake and exahaust right away. Do I need to get a Hypertech to recalibrate the speedo for the bigger tires? Will this hurt the Allison trans at all?

Once again im glad I found this forum and glad to be here!!

SteveSierra · January 27, 2002

Welcome to gm-trucks.com! This is a real good board. I think you can gain alot of info from here. About the tires. You can go to that size tire with no real problems. Maybe need some trimming of the front lower plastic trim piece or jack up the torsion bars an inch or so. If you're going to tow that much weight, you might want to consider wider rims though. Maybe 8 inch. There are quite a few options out there for 8 lug rims, just depends on personal taste. I went with 265's so I could keep the factory rims and not worry about problems towing or hauling a lot of weight. The tire manufacturers recommend about an 8 inch rim for the 285's.

There are some on here that have put 285's on the stock rims though.

You should recalibrate for the larger tires, I'm not sure if Hypertech has a programmer out for the 8.1 yet or not. They just released one for the 02 4.8, 5.3 and 6.0 engines. I'm waiting for mine to get here.

There is an issue with the larger than stock tires and the Allison trans. Actually, there is a tsb stating that if a customer brings their truck in with larger than stock tires, that the customer needs to put the stock ones back on before they will do any warranty work on the trans.

I think Airaid makes a kit for the 8.1 for intake. Don't know when K&N will release theirs. They told me 6-8 weeks. They'll probably release one for the 02's around the time the 03's start showing up at dealers. :0

Exhaust systems I'm not too sure about. I'm having a shop put one together for me on Wednesday. I'll post what I think of it Thursday. It's a true dual setup with 2 1/2 inch pipes coming out behind both sides of the rear tires with 2 Flowmaster 50 series delta flow mufflers. Probably will sound like a boat.

Have fun!

Steve

MountaineerTom · January 27, 2002

Welcome to the site. Were glad to have you here.

First off, I'd check into the larger tires issue with the Allison tranny. GM has some kind of bulliten out cocerning larger than stock tires used with the Allison. I think it has to do only with the Duramax/Alli combo though, not positive.

An intake and exhaust would work very well together if you can get one for your truck. If you do get larger tires you would need a Hypertech, or similar product, to get the speedo to read correctly. Although, I've heard it doesn't throw it off by very much. Ask StepsideZ, one of our members. He has 285/75/16's without reprogramming.

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Looks like Steve got to you before I finished.