[dmaxalliTech]

<H1>Info - Inspection of Tire and Wheel Size Prior to Diagnosis for Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns #01-03-10-010B - (10/14/2002)</H1>Inspection of Tire and Wheel Size Prior to Diagnosis of Transmission Shifts, Poor Performance, Speedometer, Cruise Control Concerns


2001-2003 Chevrolet Silverado Pickup Models


2001-2003 GMC Sierra Pickup Models


with Duramax™ Diesel Engine and Allison® Transmission


This bulletin is being revised to add the 2003 model year. Please discard Corporate Bulletin Number 01-03-10-010A (Section 03 - Suspension).


Proper diagnosis of engine, transmission, speedometer, and cruise control concerns must begin with an inspection of tire/wheel size.
<UL =BULLET>
<LI>The 2500 series trucks have LT245/75R16E tires as standard equipment.
<LI>The 3500 series trucks have LT215/85R16D tires as standard equipment. </LI>[/list]


A truck that has different tires and wheels will have Engine power/performance concerns, Transmission shift concerns, Speedometer registered speed concerns, and Cruise Control concerns.


Before any diagnosis is performed for these types of concerns, inspect the tires/wheels for the proper tire and wheel combinations.


If a truck is found to have other than the above listed tire sizes, no further diagnosis should be undertaken until the original size tires and wheels are reinstalled on the truck.


The Engine Control Unit (ECM) and Transmission Control Module (TCM) use (RPM) and (VSS) inputs as operational parameters for engine torque, transmission shifting, cruise control operation and speedometer indicated vehicle speed.


Calibrations for different tire/wheel combinations are not available.


Therefore changing of tire and/or wheel size should not be undertaken by dealerships or truck owners.<A name=ss1-1137502><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1137502&pubid=297&evc=sm#ss1-1137502" target="_blank">
<H5>Warranty Information</A></H5>


Reinstalling the proper wheels and tires on the vehicle, prior to performing any type of diagnosis of the truck, would be considered truck owner responsibility and not a warranty repair

 

[geno]

dmax


i went to 235's on my dually, got about 3500 miles on them and so far the truck seems to be doing fine, did not notice any change in any of the items mentioned, should i worry or just run it. Geno

 

[DMAX2DAMAX]

dmaxalliTech,


Thanks! I knew there was a reason to hang on to those original wheels and tires!


2DAMAX

 

[Mcfly]

I have a question about this. My truck a 3500 4x4 had LT215/85R16D tires on it. The speedo and mileage was about 3% off. This means that for the first 36000 miles I actually only drove 34920 miles. I got screwed out of 3% of my warranty. I went to the 235/85R16 and the speedo and mileage is now dead nuts on. Why would this cause issues and would GM deny me warranty coverage because of this modification?

I can understand if I had gone up to 315 or something like that

-Rick

 

[dmaxalliTech]

Rick, the only reason I posted it is because if you were to have a tranny issue or anything mentioned above, the dealer could very well refuse to work on it for that concern if the tires are not stock. It is the customers responsibility to pay to switch over to stock tire size before any diagnosis begins. It only meant as info, if you have oversize tires with no problems, run it. Just keep in mind that your speedo will be off.

 

[whiteeye42]

In your post it says that the 3500 duramax/allison came with 215/85r16D but when i got my 2002 duramax/allsion it came with 215/85r/16e why in the world would thay put a D rated tire on a 1 ton truck that pulles a big trailer

 

[FirstDiesel]

Mine came with D tires.

I think later in the model year they downrated the tires. Some people with 2002 report they have E and some have D.

 

[Mcfly]

I might have mis typed it. It very well could have been E, either way. With the two tires the load is distributed across more area so each tire caries less weight. I guess that is why you could have a D rated tire on a 3500.


-Rick

 

[RMAX]

I've seen alot of posts regarding going to 265 tires (2500HD). Anyone know how much they'd throw off the speedometer?

 

[Ray403Dmax]

There are a few handy websites out there for the speedo/rpm/gear ratio calculations. Here's one I've used in the past...


http://www.4lo.com/4LoCalc.htm

 

[Eddie Haskell]

I know not everybody has one but wouldn't a programmer fix the speedometer issue? I want to go to a taller tire to lower the rpm's a bit. When I first bought the truck (03 GMC 2500HD) the dealer told me that the computer couldn't be changed to accomidate larger tires and that the warranty could be an issue if I had problems. Somebody want to set me straight now that I already bought the new BFG'S

 

[Eddie Haskell]

t

 

[bsiler]

I have put 265 's on 03 chevy. I took it yesterday to the dealership where I bought it to talk to them about recalibration. Talked with several guys in the service dept. and they really didn't know. They talked to a mechanic that has an 03 like mine. He said that he could do it with the tech 2. He said he could do it now. Well he couldn't. The tech 2 wouldn't let him in. He called GM and they said no go. Wrong tires, They said causing shift problems with the Allison. He has had his truck a year, he recalibratrd it as soon as he got it and was able to do it then, they would let you. He said in the past year he hasn't noticed any shift problems. I don't know what to do, don't want to void the warranty,

 

[Mackin]

Many before you have swapped out for bigger tires ..... The above TSB is only in refferance to customer complaining of poor shift qualities .... GM wont address the issue without oringinal equipment ....


Going from 245 to a 265 isn't that great of a leap ,compared to what I've seen some of these guys doing .... Most dealership prolly wouldn't even take notice while in for service ....


After changing if you desire accurate speedo readings latch onto a Quad tuner or Predator for calibration purposes ....





Mac

 

[Eddie Haskell]

Like I stated I already have the new tires and between buying new, new tires and a computer tuner (which I plan on getting anyway) the cost is going thru the roof. But me, being the type that can rationalize ANYTHING said to my self... Self, people have been putting on winter tires for years so I need a set of Summer tires!

 

[bsiler]

I'm new to the Duramax. Where would be a good place to get some informatiom on the Quad tuner or the Predator? I'm sure I've read where it has been talked about before but it's easier to ask again. Just lazy in my old age iI guess!

Thanks
Billy

 

[bybycop]

Have an 03 with about 10,000 miles on it and I am starting to have shifting problems. From 1st to 2nd it is a really hard shift!!! I am running 285/60R18. So am I screwed if I dont have my stock tires??? Someone please tell me this is not so!?!


Thanks,


Mike

 

[2MuchFun]

Have an 03 with about 10,000 miles on it and I am starting to have shifting problems. From 1st to 2nd it is a really hard shift!!! I am running 285/60R18. So am I screwed if I dont have my stock tires??? Someone please tell me this is not so!?!


Thanks,


Mike

Before you take it in, I would switch wheels with a buddy for the day or two its in... Just to avoid the b.s.

 

[TheBac]

Hey guys, I found a tire comparison site....it works pretty well.


http://www.discountpartcenter.com/tirecalc.html


May want to give that a try.

 

[bybycop]

Every time I think about it, it gets me all worked up. Why on earth build a truck, a 4x4 truck for that matter, that you have to keep these small a__ tires on??? I mean im only runnin a tire that is 2 in bigger than stock and they are going to tell me that it causes trannyh problems.


Sorry, if you cant tell, Im just a bit riled up!!!! Im about ready to go back to a dodge. Seams like Im always hearing something else that will void your warranty with GM. Wouldnt be surprized if they came out with a milage limit per year or something

.


K, Now that I got that out, I feel much better!!!!


Someone please comfort me and give me good news.


Mike