Diesel Place banner

1 - 20 of 25 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
I heard a rumor a while ago that the Allisons freak out if you put over-sized tires on the truck. Is this true? Thanks.
 

·
Registered
Joined
·
3,756 Posts
I heard that they are tuned for the 245's (stock) and if you put anything else on and your Ali goes down, Allison company will not cover the tranny. Could be wrong but I got that from some guy who works on Allisons.
 

·
Registered
Joined
·
511 Posts
So how do you run larger tires?
 

·
Registered
Joined
·
274 Posts
Mine runs great! No problems at all. 285-70-17s
 

·
Registered
Joined
·
511 Posts
This issue kills me..


Maybe its just dummy me, but I cannot understand HOW the computer or transmission would have any idea of tire size as long as all four tires are the same diameter!


Yes, maybe the computer or tranny might think there was a bit more load, but that could be from going up a grade or on a sandy/loose surface etc.


~~So if all four wheels are turning in time, How can the comp. or trans. know?


BTW, I've been running the H2 315s since almost new and have zero issues.
 

·
Registered
Joined
·
576 Posts
2MuchFun,


Have you had your truck at the dealer at all since the new tires?


My stealer says I can have a 1526789624343 inch lift and be covered as long as I use stock size tires.


Basically it's a huge grey area as to coverage.
 

·
Registered
Joined
·
267 Posts
I agree w/ 2muchfun 10000000%. I've read/heard this a thousand times, but I've yet to hear WHY/HOW the Allison would care what speed it's spinning at. It might see a higher load that inticipated at say 70mph, but it's still seeing 70mph... I could see a regear in the diffs causing an issue related to ABS, but at the tires, don't see it... I've been running 285s for 25k now, been in to the dealer a couple times with no comments, and I'd love for them to start that conversation...
 

·
Registered
Joined
·
3,756 Posts
Okay, what I am saying is the OF COARSE the tranny will run on bigger tires...h--l, I am running 315's on mine. But if your Ali goes down and you bring it in with other than stock rims/tires, Allison will not cover the tranny. So, if your tanny needs work or goes down, put those stock setups back on before you get into the dealer.


My rig:



My rims/tires:
 

·
Registered
Joined
·
511 Posts
Yep, thats why my brand new set of stockers are sitting on the side of the house making me look like Sanford & Sons



And No, I have not taken my truck to the dealer with the 315s on. I went through the lemon law buyback process with Ford and I know how they can be when backed in a corner.


the Fleet guy who sold me the truck said it would not be an issue, but Im gonna be playing the ol' switch-a-roonie when I go in for service since I agree with Bodysurfer. If you give them any excuse, they'll use it. Regardless of how BS it is.
 

·
Registered
Joined
·
511 Posts
Yep, that is it, 285's are going on--as soon as I wear out those stockers!
 

·
Registered
Joined
·
420 Posts
Larger tires will ONLY affect your overall torque and horsepower. Bigger tires mean more diameter, which means more distance per turn, which means less torque.


As far as warranty is concerned, I just can't see how they can void a warranty when putting larger tires on is extremely COMMON, and expected.
 

·
Registered
Joined
·
51 Posts
Especially since GM warrants the transmission, not Allison!
 

·
Registered
Joined
·
247 Posts
I do not quite understand why people think you cannot have the Dmax/Allison reprogrammed for larger tires. I installed 265's, and had my dealer use the tech II to adjust the tires size. I checked the speedo against my GPS, and everything is right on.
 

·
Registered
Joined
·
203 Posts
265 is the max the Tech II can reprogram for based on GM instructions. The computer can handle more, but GM does not provide or authorize the larger size adjustment data.
 

·
Registered
2020 Chevy 2500HD LTZ Z71
Joined
·
644 Posts
Bodysurfer said:
...if your Ali goes down and you bring it in with other than stock rims/tires, Allison will not cover the tranny...

Great looking tire/wheel combo! Never get tired of looking at that. Remind me what part in waranty work Allison has in our transmissions. Buy a 1000 series transmission from Allison and you get an NSBU switch replaced free (national recall). Not so with GM installed Allisons. The Allison dealer is the wrong place to discuss GM warranty work. There is a reference document for this: http://dieselplace.com/forum/forum_posts.asp?TID=284&KW=allison


It, like so many other repairs, comes down to the dealer. Good relationship=open mind/common sense.


Good luck!


Kevin
 

·
Registered
Joined
·
145 Posts



Here is Allisons position on changing tire size:


Q. Speedometer / Tires - Can my speedo be re-calibrated after I install larger tires? A.
Speedometer calibrations are only available for tire sizes offered as original equipment. Please consult your GM dealer about correcting speedometer output when tire size is changed.


NOTE: Changing the calibration to correct speedometer readout does not change the TCM calibration, and thus it does not compensate for the adverse impact on transmission operation.



Back To Top Q. Speedometer / Tires - What effects will big tires have on transmission operation? A. The TCM calibration is based on factory tire size and rear axle ratio. Changing either of these parameters will have some adverse impact on transmission operation, including features like grade braking and shift stabilization. For instance, we have noted that when P285 tires are installed that the transmission generally does not shift to 5th range when towing heavy loads.


Just a messenger of info, Fran
 

·
Registered
Joined
·
511 Posts
04wanabemax said:



For instance, we have noted that when P285 tires are installed that the transmission generally does not shift to 5th range when towing heavy loads.

And thats a bad thing?


It sounds like the tranny deals with the loads placed on it appropriately
 

·
Registered
Joined
·
11,646 Posts
Boy, every thread sounds like deja-vu.....


This issue has been covered a hundred times... bigger tires, no warranty. Look at the tsb posted in the tsb section. You can risk it like alot of people do, fine. But bottom line is...... well, thats been covered before too.


~~bored with repetitive topics~~
 
1 - 20 of 25 Posts
Top