Truck Question for you Guys

[Regulator23]

Considering the massive amounts of fishing and diesel knowledge you guys have and the number of sweet rides sporting only the best SFC stickers, maybe you can help me with a truck question!

I have a 2007 GMC Sierra 2500HD Classic, 6.6L LMM Duramax, 3.73, Allison 1000 transmission. It came with stock 245/75/16R's tires which I replaced with 285/75/16R's last week. I'm no mechanic by any means and know little about trucks, so here's my dumb question.

I've heard rumors that the 285's void factory transmission warranties, and produce greater strain on the engine and transmission due to torque issues. Also, my speedometer is obviously off, and I should probably get it recalibrated. The dealer says he can recalibrate pretty well, but maybe not exactly due to the increased tire size. I think they're used to recalibrating with 265's. I also don't want to open up a can of worms with letting the dealer know I have 285's if it's going to screw with the warranty. Do I need to worry about damaging anything in the truck?

I'm considering the Superchip Flashpaq for the recalibration issues and for general performance. Are these worth the $$$?

Thanks so much for your help!

[jayjysmth]

Hey Reg,

I have an 2001 GMC 2500HD gasser w/ 285's.
I have never heard anything about voiding the warranty but I am not 100% positive.

As for the speedometer, according to my gps and truck is off by 4-5 mph.
I havent had it adjusted yet, and dont really plan to.
My thinking is, speed ticket, free get out of jail pass.

[flatbottom]

Is that an inch change or half inch change? Tell him in 20,000 miles it will be normal again just a joke. Have the guy flash in the correct tire size if it is free. What is the rears gear size? 4:11's ? 3:92? 3:73?

[Glenn W]

I have a 2004 GMC 2500HD with a Duramax and Allison. I too have heard the "rumors" on oversize tire voiding your warranty. I don't know if it's just rumors or not but the way I look at it is I paid a hell of alot of money for a heavy duty truck with diesel and the best transmission in the business. I dare (along with a pack of my Philadelphia lawyers) GM to void my warranty on this heavy duty truck because I'm running about the same size tires that come stock ( option) on Fords and Dodges.
I can see it now-- I would love to argue this one in Courst--- GM wants to void my warrany on a heavy duty truck because I am running Slightly larger tires. They say it causes too much strain on the powertrain---- yea, right.
Regarding the speedo sync-- I have 265 75's and at 65 mph I am 0.8 mph off (per GPS) Close enough for government work. I have, however heard that the 285's do cut into fuel economy a fair amount when unloaded.
Regarding the Chips--- hell yea they work. If you want to tear some shit up, go ahead put one of the real high power chips in. Great day in the morning, how much torque do you want?

[flatbottom]

He He I can see it now. Regulator23 puts a chip in. Smokes the trans. Goes in for warannty work and is denied on a 1/2 inch of tread. You got to love it there is more. Joe Shmoe pulls his travel trailer "30' " across the USA and back 3 times this summer and never changes his trans oil. Smokes the trans and they give him a rebuilt one and two front tires to shut him up Buy a tundra with the new cat engine. Problems solved did I say that

[ADDfishing]

Buy a tundra with the new cat engine. Problems solved did I say that

Don't mean to highjack, but a Tundra with a CAT???? As in diesel???? Just did a brief search and turned up nothing. Tell me more....

[Regulator23]

Yeah, jay, I was thinking the same thing, gotta love the "faulty equipment" defense.

Flat, it's the 3.73. You guys have a good point, it seems pretty ridiculous to void a warranty for an inch or so difference in tire rotation, then give the mo-ron who never changes his oil a free rebuild. Go figure.

I'm going to go with the chip then, see how she purrs. I'll admit, I don't tow very much, don't really need the torque. But hey, none of us with boats EVER go a little overboard on our toys do we?

[jacko]

I superchipped my 7.3 liter power stroke, and recommend it highly, my truck runs better,shifts better, tows better and gets noticeably better MPG. Towing a small boat to FLA, I got 16.8.

[Bird Dog]

My '03 Chevy 2500HD Duramax came from the factory with 245's. After they wore out I got 265's which the dealer put on without me even asking him to. His own demo truck has 285's on them which I plan on getting once my 265's wear out. I've never heard anything about the warranties. A buddy of mine has 305's on his Chevy 2500HD Duramax.

[GALAZIO]

Well...you're at the mercy of the dealer/service dept if they want to tag your truck as "altered". Check to see if they are having an outfit like 4wheel parts lift and put wheel/tire packages on trucks that they are selling. The shop down here is doing 20 trucks a week for the showroom floor...and the warranty is intact.

Now, if you go with 35's"...it will throw your shift points, and computer/odometer off. Some of the programmers like the Superchips allow you to make adjustment for the tires and will remap the ECU.

Here's a pic of my 2000 F-250...all the same mods and never have had any problems...the truck is fantastic. Just check with the pro's if you are unsure about the steps to take to get it right. I am sure there's a forum. I know the Ford Truck Enthuisats (sp) forum has been very helpful.