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Discussion Starter #1
New member, great site, quick question.
I want to put larger tires on my 03 Duramax, 305-70R16: 32", I had these on a 02 1500 with no rubbing or clearance issues. Also I noticed no change in transmission performance except for the Speedo being inaccurate. I overheard the dealer telling another customer you would fry Allison and computer if you ran with larger tires and no reprogramming. My opinion is it won't matter a bid, but need verification from the experts. Thanks
 

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Hooters !!!!!

Glad you jumped on board ....

No expert but it will change shift pattern .... Fry the Allison, haven't heard anyone say it has yet,I highly doubt it ... Many here are running bigger meats .... Some dealers have a policy not to address any drivability issues unless stock rubber is in place,although ... Reprograming with a Quad (preferred) or a Predator will give you the opportunity to correct speed'o and give you a tune to put the umf back in you'll lose in higher gear ratio you'll have .....

Good luck and lets get that jogger in sloooow mo ....

Mac
 

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I went to Costco today to buy a set of Michellins LTX E rated tires 265/75/16 and the salesperson told me he could sell me the tires but Costco wouldn't install them because the size was not OEM. The salesperson said it was a liability issue. I'm taking my business elsewhere.
 

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The Jogger distracted me. What was the question again.
Really don't think you can reprogram for that tire. I wouldn't worry about the Fry the Allison comment. Put then on and have fun.
 

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Discussion Starter #5
Thanks for the replies, lots of good info here.
 

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The Allison is a pretty stout unit, so I somehow doubt it would "fry" because of the tires you're talking about adding.

However, there have been a number of posts, both here and on the numerous other boards I frequent, about dealers being a PITA when it comes to warranty issues. The best, but most expensive, idea might be to get a different set of rims and mount the new tires on those. Then, if you ever need warranty repair a quick swap to the stock rims/tires could remove the dealer whining issue. But you'll need a lot of disposable $$ for that.

Since the Allison has it's own brains you might need to get 2 computers reprogrammed if you get bigger tires (the engines PCM and the trannies controller). Check out Westers Garage. Those guys do some awesome programming. Maybe they can do the Allison too.
 
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