Anyone else having transmission problems with their 4500?

I'm not a mechanic so will probably get this all messed up, but we have a 2002 4500 that I know has a Duramax Diesel and an Allison transmission (I've heard him say that enough times). The truck's a 2WD and has 0 traction in the winter, so we didn't drive it in the winter for the first 2 years we had it.

Then this winter we were going to use it to haul logs to the sawmill and ran into a problem. Seems that the computer won't let the truck move if it doesn't have enough fluid in the transmission (?), torque converter (?), which is good, but the problem is that that makes the truck pretty useless when it's cold out.

The garage says that it's because we leave the truck sitting for too long between uses in the winter, which gives all the fluid time to drain, and then it's too cold to get up to where it's supposed to be so the computer shuts the tranny down.

Does it sound like I might have described the problem correctly?

Has anyone else run into this problem?

Thanks,

Kris
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Kris Anderson
Williamstown, MA

Welcome to the Forums!

Your issue sounds normal for the early Allisons. If allowed to sit long enough, the torque converter will drain down, and prevent the tranny from engaging. You may have noticed the range selection on the instrument panel flashing when trying to select a gear.

At any rate, the procedure to use when this happens is quite simple. Start the engine and let it warm up a bit. When you are ready to move, turn it off, then restart. This will usually cure the issue for that episode. If you try to move out with the condition still existing, it may set a code and turn on the SES light. Best practice is to just start it, and let it warm up for about 5 minutes. Turn it off, restart, then continue. Also, once warmed up and driven for a while, be sure to check the ATF level. It must be checked hot, and in "P".

Quote:

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Originally Posted by DmaxMaverick

Welcome to the Forums!

>>> This will usually cure the issue for that episode. If you try to move out with the condition still existing, it may set a code and turn on the SES light.

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Yes, (big sigh), that's exactly what it does. Since the first couple times it happened we've shut the thing off and then restarted without a problem, but does anyone know what happens if it does "set a code and turns on the SES light"?

It does it all the time now, and I'm worried that I'm not going to notice one of these times, try to move it, and be stuck forever.

Kris

There's no worries with the SES. The TCM just commands the PCM to turn on the SES. The code will be P0700. The true code will be stored in the TCM. The code only "tells" the PCM there is a problem, but takes no action. It will not prevent either system from operating normally, as long as the condition is corrected. You confirm that when you are able to engage a gear range. The code will remain in the TCM/PCM for a specific number of start/warm-up cycles, then disappear. Under your circumstances, the SES is only indicating there was a problem, and remains long enough for a tech. to diagnose the issue. You can use a scanner or Tech II to clear the code, but it will go away on its own in time.

If your tranny is low on fluid, it could cause the issue to be more frequent. Make sure your level is correct.

What do you mean by "all the time"? If it is happening when it sits for less than about 3 days, it may need attention. If you don't have an extended warranty still in effect, it'll be out of your pocket. There is a bulletin and repair to address the issue. But...If it were mine, I'd live with the issue, as it will cause NO long term effects. I couldn't justify the cost vs. effect. The only thing suffering is convenience, although it doesn't make it right. If you decide to have it corrected, don't go to GM. Have an Allison repair facility do it. The cost will be about 1/2, and they'll do it right the first time.

[QUOTE=DmaxMaverick]There's no worries with the SES. The TCM just commands the PCM to turn on the SES. The code will be P0700. The true code will be stored in the TCM. The code only "tells" the PCM there is a problem, but takes no action. It will not prevent either system from operating normally, as long as the condition is corrected. You confirm that when you are able to engage a gear range.

The first time this happened the truck was parked in front of a wall and wouldn't go into reverse, so we were stuck. The mechanic did come down and clear the code so we didn't have to have the truck towed, but my worry is that I'll get in the truck some day and try to drive off, and get locked out of the gear I need to move the truck.

>If your tranny is low on fluid, it could cause the issue to be more frequent. Make sure your level is correct.

It's been checked numerous times, both at home and by the dealer's mechanics. I think the mechanic changed it last time we took it in, but I'm not sure of that.

>What do you mean by "all the time"? If it is happening when it sits for less than about 3 days, it may need attention.

It did it again last weekend after being driven for about 20 miles and then parked for about 3 hours.

>>>The only thing suffering is convenience, although it doesn't make it right. If you decide to have it corrected, don't go to GM. Have an Allison repair facility do it. The cost will be about 1/2, and they'll do it right the first time.

Thank you for that advice! The truck is off warranty so we'd have to pay for it, although the mechanic who worked on it said that as of right now the only "fix" they have is very expensive and doesn't really fix the problem, anyway. GM is supposed to be working on a more affordable fix, but I'm hoping that the truck will be gone by then.

Kris

It won't strand you. Once it has ran a little while, the converter will fill up, and you'll be able to move it, normally. The problem is, the TCM expects to see certain pressures, and doesn't get them at the time, then defaults the tranny. That is why it is fine after a restart, even if there is a code and SES. This happening after only 3 hours of sitting suggests the issue is more serious than the norm, but still the same issue. Have you changed the external spin-on filter lately? If not, do that before anything else. Once plugged up, they can cause several issues, including cold start, no-go.

One reason I suggest having an Allison shop do the repair is evident by your "tech's" statement. There is a fix for it, and a good one. GM has been doing it for some time now, and any Allison shop will know what to do without trying to locate some GM bulletin. The fix is simple, and [supposedly] permanent. The problem and cost factor is the labor involved. If you have a good relationship with your dealer, try to get them to help you out with it. It is a known issue. If you have ever complained about it, to them, and before your warranty expired, they have the ability to warranty it. They can do it. It just takes a little initiative from your dealer.

[QUOTE=DmaxMaverick]

>It won't strand you.

Then in that case I'll stop worrying about it! We've been talking about trading this truck in, but if it's not going to strand us somewhere then I'm okay with it the way it is.

Either "fix" (trading it in or taking it in) is going to be expensive, and it's been a pretty good truck so far, except for the poor traction and this transmission problem.

>Have you changed the external spin-on filter lately? If not, do that before anything else. Once plugged up, they can cause several issues, including cold start, no-go.

I'll check, but the truck goes in for maintenance regularly, and has been in for even more maintenance since we started dealing with this problem, so one would think they would have changed what needed changing! The truck now has about 17,000 miles on it, and most of those are trip miles.

>One reason I suggest having an Allison shop do the repair is evident by your "tech's" statement.....

Thanks for the further information. We kind of felt that GM should fix it, since the truck obviously had the problem back when it was still on warranty and they know that, but I have a feeling that's not going to happen.

The way the dealer described it the fix involved taking the truck all apart to get to the part they needed to fix, and then the fix wasn't even guaranteed to work. GM was supposedly working on a more affordable "fix".

We will definitely take it to an Allison shop if we do decide to have it worked on, though. Our next step may be to take it to an Allison shop and get an estimate, which we can then carry in our hot little hands when we go see the dealer again.

Thanks again for the scoop on this whole thing. I'm not a mechanic, but I know several who are interested in what's going on with this truc, and they're going to be very interested in this information!

Kris

I had the same no go problem with my 02 duramax allison. Took it to the stealler and was told I needed a park neutral position switch replaced. I waited and did some research first. I was able to contact a friend who can look thru a GM electronic repair/bulletin system. He faxed me bulletin #02-07-30-011C dated June 21, 2004. It is a replacment they call the transmission position switch/sensor. It's the external component where the shift cable connects to the trans. The bulletin describes that the front left tire throws water directly at the switch on turns. The replacement has a front and rear shield to prevent this. Switch kit # 29540479. After reading your info about the converter drain down I wonder what the problem really is. What is the fix you speak about at an allison shop? Let me know if possible so I can persue the correct repair.

jlavin

There have been issues with the early NSBU's (Neutral/Start/Back Up), and you found the correct remedy for it. The problem is more of snow/ice packing up around the mechanical input of the switch, and not so much just water. If you have to buy one, get it at an Allison dealer and save yourself about $100 over the GM parts counter. Kris55's issue doesn't appear to be NSBU related, and his rig is a 4500, which, for whatever reason, hasn't really had the NSBU issue. Probably due to its late introduction, and incorporation of the newer NSBU, and possibly due to the location of the switch in relation to the wheels, compared to the pickup models. The repair for the drain-back involves the repair/replacement of a ball valve inside the tranny.

If you are having issues of the tranny not engaging into a gear, usually accompanied with a flashing, or no gear indicator on the instrument panel, the problem is likely the NSBU. There should be a DTC for either problem, and that should tell you which is you actual problem.

Hey, I was able to call the GM 1-800 Number and ask about covering the part under warrantee. My truck is still under the emissions warrantee and listed under the items covered is a neutral selector switch (or something close to that, check your warrantee book). Anyway, at first they said it was not covered but when I pushed the issue and asked again it got fixed for free! Problem solved.