<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&amp;pubid=297&amp;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

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

dmaxalliTech,


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


2DAMAX

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

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. http://www.dieselplace.com/forum/smileys/Approve.gif

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 trailerhttp://www.dieselplace.com/forum/smileys/Approve.gif

Mine came with D tires. http://www.dieselplace.com/forum/smileys/Cry.gif





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

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

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

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

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'Shttp://dieselplace.com/forum/smileys/Ouch.gif

t

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,

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 http://www.dieselplace.com/forum/smileys/Approve.gif

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!

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

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

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.

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.

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 somethinghttp://www.dieselplace.com/forum/smileys/Cry.gif.


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


Someone please comfort me and give me good news.


Mike

I keep running this through my mind also.


If you have 4 wheels and tires that are all the same size, how can this affect anything?? The computer is just reading how many times the damn wheels go round and round, it doesnt know how far the vehicle is moving with each revolution!


I could see if the tires were different size but...


Now what happens when you wear the tread down 6/32, does that throw something off and cause a fault?


this sounds like pure B.S. to me!


Its like when the power window motor goes out and they blame it on tinted windows!! http://www.dieselplace.com/forum/smileys/Angry.gif

I had tranny issues before I took off the 245's. Changed the Internal filter and replaced fluid With Valvoline Dex 3. All is smooth now. Changed tire to 265 about 4K ago. No problems. Less than 1" in Diamater increase. Can change that with air pressure. Go figure.

ya, I think its a bunch of poppycock. BUT, I guess I'll have to keep my old rims and tires around.


I would bet though that if you are having shifting issues with larger tires and you switch back to stock size, the issues will still be there..

Yall are gettin worked up for nothing on this.. Go ahead and change the tires, it aint likely gonna make a difference, but be ready for a run around with most dealers for a concern that requires diag. If they have to call tech assist, one of the things they ask in every case is if the vehicle has been modified in any way, if they say the tires are not oem size, game over until they are.

Yall are gettin worked up for nothing on this.. Go ahead and change the tires, it aint likely gonna make a difference, but be ready for a run around with most dealers for a concern that requires diag. If they have to call tech assist, one of the things they ask in every case is if the vehicle has been modified in any way, if they say the tires are not oem size, game over until they are.


And thats not something to get worked up about?

not if you dont have a problemhttp://www.dieselplace.com/forum/smileys/Embarrased.gif

not if you dont have a problemhttp://www.dieselplace.com/forum/smileys/Embarrased.gif


Ok, true http://www.dieselplace.com/forum/smileys/Embarrased.gif


Im going to the H2 pulloffs but Im saving the originals just in case

I am having a problem though. My shifts are very hard and abrupt. Do I try going in to the dealer and have them check it out and not worry about going back to stock until they say something??? Or will they not give me a second chance once they know i was running bigger tires? I dont mean to make a big deal but now that my tranny is acting up Im a little worried.


Thanks,


Mike

Personally, I would go back to stock before going to the dealer. You will also be able to see if going back to stock does anything to correct the problem shifts. I really doubt it. I have a very hard time understanding how the tire size would affect shifts... but ..

I think what GM is worried about is the guys that are running big tires on the highway and not pulling enough rpms to allow the tranny to lock up. This would cause a lot of stress/heat in the transmission.

bybycop,


I would DEFINATELY put the stockers back on before I took it in. Better safe than sorry.


Those allisons are EXPENSIVE to replace or rebuild. Unless you were going to put in a Suncoast anyway.


Just think stealth...What they don't know won't hurt your wallet. To me Tire size is a little different than some of the mods that I have seen done. I mean if a guy with NOS melts a piston I think he should pay for it. But by just running a little taller tire. That is a GM design flaw! IMHO


Mike

Well, I finally put on a set of H2 take offs. No problems with shifting whatsoever.


.... I am keeping the stock set just in case

I also have H2's with 265x70-17 Revos - no problems to date. I thought about putting my stock take-offs on ebay, but I may just hang onto 'em...


Why GM built a big truck like this with Honda Civic wheels/tires is beyond me. http://www.dieselplace.com/forum/smileys/Disapprove.gif


Chris in NC

Where are you guys finding these H2 "takeoffs", and are they priced reasonably. Anybody got a photo so I know if I should persue them


eddiehaskell@sbcglobal.net

I just read this entire thread. I have an 03 with 20K miles. The interesting thing is that I took delivery from the dealer with 265/75 BFG's - asked them if they would swap out the stock tires and they were perfectly OK with it. They swore up and down that they would not have any problems honoring my warranty because of his.


The service department is also OK with it - one tech has a dmax with 285's so 265's were no big deal to them.


My shifting and ABS have been fine. My speedo is off by 3.5% according to GPS. Just have to remember that 75 is actually 78!


One other weird thing - my odometer is "slow" by 5%. Verified with maps, GPS and other vehicle odometer. Strange for it to be off more than the speedo. But I really don't care I'm putting 5% less miles on odo....


FWIW, Dealer is Kool Chevrolet in Grand Rapids, MI.


Fred G

Where are you guys finding these H2 "takeoffs", and are they priced reasonably. Anybody got a photo so I know if I should persue them


eddiehaskell@sbcglobal.net








Here's a picture of mine, but they're dirty as heck and my truck is on uneven ground so you cant really see the look at level.


http://dieselplace.com/forum/forum_posts.asp?TID=4171&amp;PN=1


Im running the 315s that came on the rims.


I got them from a guy in Thousand Oaks CA.


Just call around to the Hummer dealers and ask about them. They're going for around $500

I am new to the forum and just wanted to give some information from my own experience. I have a GMC Sierra 2500HD C.C. S.W. 4X4. I drove it from the dealership to a Firestone Dealer and replaced all 4 tires. I choose the Bridgstone A/T Revo LT285/75R16. This size to me looks and fuctions the best. However after installing the tires I noticed the front tires rubbed slightly on the bottom corner of each side of the bumper. All you have to do is have your tortion bars tightened to raise the front about 1 inch. This also levels the truck. After doing this you will have to have your front end realligned. I am glad that I did this because the front end was off from the factory. I also purchased a Hypertech Power Programmer III Part#30021. The programmer has a feature that allows you to change the tire size to just about any size. It also has 3 different H.P. and Torque settings to choose from. I now have about 15000 miles on my truck and have had no problems at all. My speedo is right on the money. Hope this bit of info helps.

I wonder if they made some changes, my 3500 SRW is supposed to come from the factory with 265's.

2 Muchfun...... thats a sharp truck! The wheels were 500 bucks for all 4?

I was looking for larger rims for a 3500. I was at a rim dealer and he stated that ford is running a 19.0" or 19.5" rim with the same bolt pattern. I am seriously looking at trying to stick this larger rim on my truck.


I am wondering if any programers will allow for a calibration to this large of a jump. Does the programer need to have the Tire Diameter or the actual Tire sizes to make the recalibrations. I will probably use the same size tire but on the 19.0" or so rim.


Does anyone have some input on this idea?

Yah I have the same question as Toyota...


Lets say I want to run the 22.5 alcola's on my truck,what would I need to do to do this?

I asked my dealer about this and he said that "no GM trucks have come with 265's, so they could not reprogram it" Is there any RPO for the 265's on a GM truck? If so I will bring that in and have him look it back up.

IIRC, they come only on the 3500 SRW with steel wheels. Since the Tech II will look at your truck's serial number, if it's not a 3500 SRW, it won't allow a re-program.


GM got really stinky about the changing tire and/or wheel sizes not too long ago and has advised dealers to not troubleshoot any driveability concerns unless the stock sizes are on the truck. Some dealers will still trouble shoot stuff, but may not repair problems unless you're stock.


Just something to think about...http://www.dieselplace.com/forum/smileys/Ermm.gif

What do you think happens when a Regency conversion truck purchased new with 285's has driveability problems? Does GM or Regency or who cover the warranty?

This may be a stupid question, but I really don't know.....


If I'm running 315-75-16's on my truck I know the speedometer is running slow.....when it shows 60, I'm actually doing 68, but is the odometer recognizing too few miles or more than I'm actually doing. Thanks for the help clearing this up.


Chris

Less, same as the speedo. It's a free extended warrantyhttp://www.dieselplace.com/forum/smileys/HiHi.gif, unless you run out of time first.

Yall are gettin worked up for nothing on this.. Go ahead and change the tires, it aint likely gonna make a difference, but be ready for a run around with most dealers for a concern that requires diag. If they have to call tech assist, one of the things they ask in every case is if the vehicle has been modified in any way, if they say the tires are not oem size, game over until they are.


DMaxAlliTech...Sorry so late posting about this, but I just got on the forum and I hope you will see this! I have a couple of questions. Why is it that 2500HD and 3500 SRW get 245's and 3500 Dually's get 215's from the factory and they claim that going up to a 245 for a dually is going to stop them from diagnosing a tranny problem? And...now that I hear an ECM can't be reflashed with a correct tire size, does that mean they get different ECM's? And if they do, what would stop someone from swapping ECM's? Just curious...because I was planning to go up to 245's on my dually figuring I wasn't going to harm anything since the 2500HD's have that size and the drivetrains are identical. Edited by: CrazyDaze

I can't for the life of me figure out why tire size would affect the troubleshooting of shifting problems. The engine speed to rear axle ratio remains the same no matter what size tire is installed. The only thing that changes with larger tires is ground coverage (speed) per revolution. The engine and tranny load would only increase VERY SLIGHTLY to rotate the additional weight in rubber but are these trucks not advertised, built and sold for work. The only explanation for this TSB would be to again pass the blame on to the consumers who know no better. I would not hesitate to install larger tires because I know it will not cause problems but this buisness tactic dreamed up by GM is a shame to say the least. The trick is to pass on as much as possible cost/liability to the customer while maintaining market share of truck sales. http://www.dieselplace.com/forum/smileys/smiley18.gif Edited by: a bear

Up where I am the 3500 without duels come with 265 and the 2500s have 245. Same friggin truck only 1 has heavier rear and susp. The 245s look cheezy as hell. The ones that came on my truck had car treads.

It's kinda funny that they (GM) would make a big deal about tire size changes. They designed these trucks to tow 15000+ lbs and say if you change the tire size they could void your warranty. As if an inch or 2 bigger is going to make that much difference. Anyway, I ordered 285s for my truck, but I am going to keep the 245s just in case. (for driveability problems at the dealer)

Just to put in my 2 cents, I got a 3500 SRW in June 2004 and it came with 265/75R16 and I haven't had any problems.

I changed to 265's with all of 100 miles on my '03. Now have 34k miles with no problems to report. I have not done anything to re-calibrate the computer, just have to remember it reads a little low ;). I do have the infamous 'clunk' in the steering...sigh. Now have a knock in steering (had in '01, they changed an idler arm or something on in...had 285's on that one and they did not give it a blink...the tech's actually thought it looked good with them) so will take in before warranty expires.

-DMaxEnvy

I move to 265 Michelins from the 245 Firestone at 5K. See about 1- mph difference at 60. You will need to look at a tire loading chart. Both Goodyear and Michelin have them on the web. You may want to reduce the pressure slightly. Still gives better handling and stopping.

The reason I switched (the first time I have ever changed OEM tires early in life) was the lackof wet weather stopping traction of the Firestones. GM has missed the boat. The 245's will handle the load fine, but do not have enough road surface for a vehicle this heavy.

I move to 265 Michelins from the 245 Firestone at 5K. See about 1- mph difference at 60. You will need to look at a tire loading chart. Both Goodyear and Michelin have them on the web. You may want to reduce the pressure slightly. Still gives better handling and stopping.

.what pressure do you run in your 265's? anyone out there with 285/75r16 what pressure do you run on the street?

I've seen alot of posts regarding going to 265 tires (2500HD). Anyone know how much they'd throw off the speedometer?
My 04.5 HD DM has 265 Toyos and the speedo reads about 2.5 MPH slower than the GPS.

Bob

After reading this post it sounds like the Ally tranny is a pansy? You are scaring me to death! I drive by lifted Dodges and Fords with 36" swampers on them all the time! I am running 285 75/16 on my truck. What should I be looking for as far as problems go? It seems to shift very smooth but I don't usually put it under much load. Has 40K miles but purchased used so I don't know how long they have been after stock tires. Is this tranny issue really that serious?

After 65,000 miles on stock tires, I replaced them with 265's. About a month later I started having trans problems. The shifting has become erratic, particularly when accelerating. It's been to the dealer for service; they didn't find anything wrong, and said that changing gears at 3000 rpm is normal. I wouldn't think that changing tire sizes would make any difference, but I'm at a loss for a better explanation. Guess I should have saved my original tires...

PArent, its not that the allison is a pansy tranny, its the fact that GM will use any excuse or opportunity available to get out of covering warranted items..... Dont worrry with 265's

Ogre, thanks. When it's time to replace my tires should I consider going from 285's to something smaller? I think the stock 245's are too small!

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I ran the Michelin 265's for 50k on my '02 with absolutely no issues. It was a gasser, and I know the Allison is a different animal, but I just bought my '05 in December and the dealer did not hesitate to put the 265's on her! I even have the paperwork showing the change. They were just worried about the load range matching the factory 245's. This was long after the service bulletin!

As for pressures, I run 55psi in all for daily driving. When towing I run the rears up to the 80psi recommended.

I put 265 BFGs on my truck 5000 miles ago when it had 20,000 miles on it. 2004.5 HD 4x4 with everything else being stock. I also replaced the rim and went with MB Motoring 8" instead of the 7.5" that came on it. Since doing so, I've lost 2 miles per gallon and the truck is now a dog. Not terribly doggy, but not as snappy as it was with the 245 pizza cutters. I'm wondering if going back to the stock rim would help as the extra .5" rim and the offset stick the tires out more than the stock rims. I still have the stockers so it wouldn't be much of a change to go back. Any thoughts?:help:

You shouldn't have that much difference in driving power. I think the stock rims on the truck were 6.5" wide. At least that is what the tire place told me since they were putting on my 285s and they are recommended to be put on 7-9" wide rims. I put 285s on mine and noticed very little change in power. Just buy a programmer like a bully dog and at the 40 hp setting, mine feels faster than it did stock. Other than that, I don't know what to tell you. It is a trade-off, but more for some. You have the Duramax in your truck? I know more people may chime in if they know what engine you have in your truck.

Thanks for the thoughts. I have the Duramax and allison. I couldn't believe the difference in performance. I was also disappointed that I had to raise the front-end as I am short and now it is harder to get in and out of the truck. Steps are next and I think I'll go back to the factory rims so that I can lower the front end back down. The 8" rim and the offset stick the tires out past the fender wells and also rub the front air damn. So, by going back to factory, maybe I'll get my performance/mileage back and be happier. I do like the looks of my MBs though. Hard to know what to do.

crghill,

Are you accounting for the fact that your tires are about 5% larger? If your odometer says you went 100 miles, you actually went 105 miles. Try recalculating your mileage with this in mind, maybe you didn't really lose 2 mpg's?

Do you think this issue is a mute point now that the 3500srw has 265's from the factory?

Thanks for the thoughts. I have the Duramax and allison. I couldn't believe the difference in performance. I was also disappointed that I had to raise the front-end as I am short and now it is harder to get in and out of the truck. Steps are next and I think I'll go back to the factory rims so that I can lower the front end back down. The 8" rim and the offset stick the tires out past the fender wells and also rub the front air damn. So, by going back to factory, maybe I'll get my performance/mileage back and be happier. I do like the looks of my MBs though. Hard to know what to do.
what was your backspacing on those 8" rims? Ive heard its best to go above 5" of backspacing.....

I don't know the backspacing. What is backspacing?


thanks!