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Bigger Wheels and Tires


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Over on the GM Diesel page there is a discussion on putting bigger wheels and tires on 3/4 ton pick-ups with a allison trans.

 

Quoting a service bulletin that says GM strongly discorages this practice. Have any of you heard of such a bulletin? :sigh:

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Over on the GM Diesel page there is a discussion on putting bigger wheels and tires on 3/4 ton pick-ups with a allison trans.

 

Quoting a service bulletin that says GM strongly discorages this practice. Have any of you heard of such a bulletin?  :sigh:

 

 

 

 

I think there is a TSB out about it. If the truck has larger size tires on it and there are problems with the transmission that the transmission is not covered under warranty.

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From what I have heard or read, they can refuse warranty because of bigger tires. I see it all over though. I, myself wouldn't mess with it, but do what you want. There are plenty of people out there running big tires with the Allison.

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From what I have heard or read, they can refuse warranty because of bigger tires. I see it all over though. I, myself wouldn't mess with it, but do what you want. There are plenty of people out there running big tires with the Allison.

 

 

 

 

 

Why would and why do dealerships refuse work? Why do the stealerships care what the cause is?

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From what I have heard or read, they can refuse warranty because of bigger tires. I see it all over though. I, myself wouldn't mess with it, but do what you want. There are plenty of people out there running big tires with the Allison.

 

 

 

 

 

Why would and why do dealerships refuse work? Why do the stealerships care what the cause is?

 

 

 

 

 

If it's under warranty it costs them. I'm not sure exactly how it works. I don't think they pay for parts and maybe they are compensated for labor but that still ties up a mechanics and man hours when they could be doing something that pays or earns them a profit?

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I've been thinking about going to 265s on my 2004 2500HD with the Ally. I would be very interested to know what the real world experience is for those who have upsized and how many of you have reprogrammed the computer after upsizing. I've read on some other forums that it isn't a significant enough of a change and that you only need to update the computer if you are going to 285s. What has been everyone's actual experience from you who have upsized and have you experience tranny shifting problems if you haven't reprogrammed?

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This topis seems to be one of the most vague areas for the Allison tranny HD owners. I see alot of HD's running the roads, mainly with 285's, a hand full of 305's, and even a couple with H2 take offs.

 

I know the major concern is the tranny working overtime to compensate for the larger diameter wheel, but would a custom tune, compensating for the tire size change, and corresponding shift points, negate this strain on the tranny?

 

As previously posted, I was concerned that my 8.1 , Allison, with 3.73's would pay the price if jumped to 285's from the 245's, and the more research I do, the more confusing it gets. I know people have posted the problems with dealers not addressing tranny problems unless the owner swaps back to stock 245's, but this doesnt make sense because one would assume the dealer could determine larger size tires were used based on the trimming and cranking typically done to accomodate larger tires.

 

My truck is a daily driver, with next to no towing, and I hate the look of the 245's. I know MPG sill suffer at first, but Im thinking that a custom tune such as Westers could correct this, and get it back to normal MPG wise, and maybe a little better.

 

As with most searches, it seems the more you research, the more your confused. I know the deisels run the same 3.73's, which I assume were designed for towing, but I cant see how juming to 285's is any worse than dragging around a 9000 lb trailer all day?

 

Any horror stories on the Allison failing prematurely, and if so, do you think it was tire related? Or are all the people running the 285's pressing their luck and asking for trouble. Id hate to settle for the 265's, but if this is the logical consensus than I guess it's the right decision.

 

Sorry for the long post, any input as to the correct setup is appeciated.

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I have been running 265's for some time now with absolutely no issues at all. I have the PCM reprogrammed to account for this. I prefer the 265's over the 285's simply because there is a little more clearance and not as much torque loss. Tranny shifts fine, doesnt heat up, and seems to pull just like it did when it was new. You can see pics of my tires if you click on the link in my sig.

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My 2006+ Duramax LBZ/Allison will stay bone stock, pizza-cutter tires and all.

 

I'm not going to take something that isn't broken and mod it until it is.

 

Steve

 

 

 

 

And thats your right as an American citizen.....to choose what you want to do. Its funny, i said the same thing in the first few months of having my truck. Then i went to the track with a buddy of mine, i got the bug.......and the rest is history. Mine still runs as good (way better) than it did the day i bought it.

 

Hey dogzapper, just wondering if when you typed your response you may have been banging your fist on the table at the same time? :sigh:

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Get whatever size tires you want, and some custom rims or someones stock take-offs. Then keep your originals and throw them on anytime you need to go to the dealer. Problem solved, you get the looks and warranty.

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Get whatever size tires you want, and some custom rims or someones stock take-offs.  Then keep your originals and throw them on anytime you need to go to the dealer.  Problem solved, you get the looks and warranty.

 

 

 

Yeah, in a way they asked for it with the miserable way they're dealing with the steering shaft. What comes around, goes around.

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It seems a bit strange that the Allison is rated so highly if this is all it would take to screw it up.

 

Then God forbid if you are a rancher and you pull a stock trailer full of steers......An oil field worker hauling heavy drilling equipment....Or even Mom and Pop hauling a big fifth wheel holiday trailer.

 

To be honest I have heard crap like this so many times over the years with Big Tires on Camaro's, Nova's. etc. and not once have I ever had a problem.

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