ArthurW

I couldn't see any twisted lines originally, I haven't had a chance to look again since. This other dealer is much easier to work with, and they said they noticed the code right away. It wasn't setting off the CEL but they scanned it anyway and it was there. Sure enough, I drove the truck home today and the shutters were closed. The other times I've checked they've been open but maybe they just weren't stuck at that moment. They said the shutters need to be fixed regardless, but yes it can affect transmission temps just because of the lack of airflow over the transmission cooler. He said if the shutters don't fix it, then they'll move on to other things (gotta start somewhere.)

Quick update - the other dealer took the truck in a day early (I had left it with them for a couple days while I was away on a trip) and they got back to me saying there was a code for active grill shutter performance. They think the shutters were periodically sticking causing the issue (which could make sense). They've ordered them, and are trying to source one from another dealer as they're on backorder. While I'm not certain this will 100% fix my problem, it makes sense and I have a much better feeling about this dealer rather than the incompetent bunch of monkeys at the other dealership.

Just as a FURTHER update for this, this is the latest email I got from the "GM Support" email from above (end of about 15 back and fourth emails of me explaining the issue trying to come to a solution). What kind of load of garbage is GM's support if they think this is an actual acceptable solution. "Just keep watching it, and when it acts up again go into the dealer for the 8th time and see if they can see anything" At this point, I've been a GM guy my whole life, I think this may be the end for me. Unbelievable. The truck is currently at another dealership, we'll see what they can do.

I was literally just about to ask if there's any GM techs with first hand experience on these trucks. lol.

I'm actually looking at the alldata description for removal/replacement of the cooling lines and they look to be all metal lines on my application. I'll follow up with what I find.

I'll do that this weekend, and see if I can find anything. I appreciate it a lot.

The picture provided in the TSB isn't very good: But I'm going to have a better look at it sometime this weekend and see if I notice anything.

Thank you. I printed this bulletin a few months ago and gave it to the dealer three times now explaining this matches my condition and they should read it haha, clearly they haven't considered it yet.

Lol me neither, I'm a really agreeable guy but this is just getting to the point of being ridiculous and I'm beyond frustrated. I feel like I've tried everything and gone out of my way to try and help. I haven't reached out to the general manager. I have been dealing with the service manager. I believe if it's anything like the service department will be fruitless as well. I live in Canada, we really don't have much for lemon laws, but I do have the ability to deal with CAMVAP (which I'll avoid for now as it really seems to be a biased system) and just flat out taking them to court which I guess is an option and fortunately for me my wife works at a large legal firm so access to lawyers won't be an issue. I'd prefer to just solve the issue, so for now I think my next best course of action will be taking it to the next closest dealer (about 45 mins from me) to have them look at it and see if they can come up with something. I mean, if it comes to going Def-con 5 so be it, but I'd really rather not. EDIT: I appreciate the kind words though, it reassures me that I'm not being unreasonable here. My good nature makes me feel guilty after an hour or two of cooling off lol.

After our argument today I doubt he's going to be helpful to me at all lol. Yes, I have everything documented and that's my only other plan of action which is to take it to a dealer about 45 minutes away from me to see if they can give me a hand on it. The dealer I'm dealing with now has a reputation of being TERRIBLE to deal with, (now I find out about it lol) but apparently the one down the road might be better, so I guess I'll give them a try. That said, I shouldn't have to, this should be a fairly straight forward escalation process. *shrugs*

Just as a further update, I took the morning off work to make a trip about an hour away to get the transmission hot to help the dealer diagnose this issue. I loaded my tractor on my trailer the night before and hauled it from 7 a.m. to 9 a.m. for them to diagnose the issue when I got there. Their technician looked at the truck, took it for a drive, and came back, saying that I had overloaded the truck and that the trailer was overweight, causing the issue. I adamantly disagreed with them and got to the point where the manager offered to call DOT to have it scaled to prove his point. He attempted, but was unable to contact DOT. I took initiative, got the truck scaled at a local gravel pit, and brought the dealership the scale ticket for the truck and trailer. My trailer and truck combined were 11,760 lbs. My GCWR on my truck is about 15000, so I am not overloaded. They agreed that they could see that the transmission temperature was continuously rising but had no code to go off of. I heavily suggested (I was angry) that they should consider the TSB that explains this issue and that the next logical solution would be the thermal bypass valve (valve body) (which they claimed they ordered but apparently didn't) or even to just check the cooler. The manager was very adamant that he couldn’t do anything. This needs to be resolved by GM. I am obviously not doing this for fun, and I just want to be able to haul with my truck without the transmission overheating. To summarize my experience today so far: I spent $100.00 in fuel for GM to once again waste my time (the only purpose of this trip was to help the dealership diagnose this issue) (250 km). Take the morning off work to help GM diagnose the issue. Load my trailer with my tractor the night before (taking it out of winter storage solely to help GM diagnose the issue). Be blamed for overloading my trailer when it 100% wasn’t. I clearly explained to GM that this happens with any trailer (my utility trailer is empty (2500 lbs), my camper (5500 lbs), or in this case, my utility with my old tractor (the combined gross weight of the vehicle and trailer was 11,700 lbs (call truck 4500 lbs on the light side, so trailer at 7200 lbs). To prove my case above, I have provided in previous emails to GM Customer Support and to the service manager, the registrations, including the weights of my trailers, so as to help my case. After our argument, I took time to get the truck scaled at a local gravel pit to prove them wrong and further my diagnosis so they couldn’t just push it off. I was apparently lied to by the manager about my valve body being ordered two months ago, which I’ve been patiently waiting for, but apparently nothing was actually ordered. This is now the 7th visit my truck has had to the dealership, with no end in sight. The manager has promised me he will reach out today to confirm the next steps of action (but I doubt there’s going to be anything, if he even calls) It is absolutely ridiculous that this much of my time is being wasted. Every single time GM asks for something to help with the diagnosis, I help, but I am getting absolutely nothing in return outside of headaches and frustrations. GM, please step up and help me fix this vehicle or buy it back/replace it so I can get a replacement that won’t cause me these headaches.

That is the plan for tomorrow, I threw my tractor on my trailer and I am going to tow that tomorrow to work, sneak out for a couple hours, drive it for an hour or so and dump it off at the dealer for them to look at it. Beyond that there's not much else I can do. I doubt they'll give me a tech for 1.5-2 hours lol.

Yeah, I did check for lines quickly when the dealer didn't do anything for the second or third time, I didn't see anything but next time I guess I'll have to open up more of it to get a clear view. I'm fairly confident that it's the faulty bypass, but we'll see where that goes.

Don't get me wrong, they have tried that and claim to have software they can use to replicate trailering, but they've had no success in finding anything. My last thing I'll be able to do is bring it to them while it's overheating, although I'm fairly confident it's a mechanical problem that won't be observable on software (bypass valve, like the TSB says lol) but at some point someone with some power has make this right.

Good thought, I don't think I've actually ever looked. The engine never overheats, but I'll definitely check that when I get the transmission to overheat again.

Yeah that's my next plan - just have to arrange a day I can get off work to do it. Beyond that, I'm not sure I can do anything.

Thank you, I really appreciate the words. I'm at a loss as to what I'm supposed to do in this situation. With the holidays coming up this is only going to get prolonged so I assume I'll be on the waiting list again. No initiative taken from the company to source a trailer, or to replicate the issue other than them just driving my truck around the city and expecting it to show signs of overheating (which I told them it wouldn't unless they were towing.) I really had hoped that GM would be an advocate for helping me get the issue solved whether that meant getting someone to drive my truck with a trailer for a couple hours, renting a trailer, or doing anything to help resolve it. Right now there really doesn't seem to be a plan, just a "when it's doing it bring it to us" which isn't exactly easy with a 25ft camper. Anyway, guess I'll just hope I can make it out of province with this thing with minimal stops for overheating (I expect several lol), I'm just disappointed in the company.

Hey, no. My dealership seems to be completely useless - I haven't been able to get them to do anything. For the last few months they were "waiting on parts" because supposedly they had ordered the valve body, and after a nasty email I sent to GM support the dealer contacted me saying they wanted to "put this thing to bed" and were going to look at it this week - they looked at it today and again couldn't find anything. So now, I'll definitely have to bring it to them overheating. This is ridiculous, I can't understand how a dealership can be this problematic. I spent a ton of money on this truck, and for them to have no solution to the problem is ridiculous. I'm taking the camper to another province at the end of the month, so I fully expect to overheat it multiple times on the way down there, and when I get back I'll have to bring it to them when it's overheating. This may end up having to go to a lawyer, because I just want my truck to function properly. I even threw it out there that if they could buy it back, I would purchase a higher trim nicer truck from them, but obviously to no surprise it was ignored. I guess we will see with the next visit, or I'll have to stop at a different city's dealership and see if they can figure this thing out, but if not I don't know what other option I have. We're at 5 visits for the same problem, and 10,000KM and still nothing has been done other than "topped up fluids". It's not like I'm doing this for entertainment, I want to haul my camper without worrying about overheating the transmission and sitting on the side of the highway. Sigh.

Thank you for this, this is exactly what I'm looking for so as I continue to argue with my dealer to get this resolved I have some comparable data. Thanks, I was sure I saw that somewhere. Agreed, after some thought, I won't be touching it until they have it fixed.

You may be right, I was thinking that this actually attached to the thermal bypass, maybe you can bypass it from the outside of the transmission. My original thought came from the bulletin from GM: "The Thermal Bypass Valve (TBV) may be the cause of the overheat if a cooler line is not twisted or misshaped. The TBV will open at the following temperatures for the models listed in this TSB. 6 Speed (6L80, 6L90) - 158F (70C) - TBV is external to the transmission. 8 Speed (8L90) - 194F (90C) – TBV is external to the transmission. 10 Speed (10L80, 10L90, 10L1000) – 143F (61C) – TBV is within the valve body on all listed applications except those equipped with 3.0 (LM2) Diesel. On the LM2 Diesel, the TBV is external to the transmission." Good call, I will buy it if it'll cool down the transmission.

Appreciate the thought, but this only works for the 3.0 Duramax. The thermal bypass valve on the 10L80 attached to the 5.3 is internal to the transmission and would entail replacement of the valve body I believe. As an update to this whole ordeal, I took the camper out again last weekend and the transmission overheated again. This time went to 132C (270F) before setting off the alarm for "Hot transmission - idle engine". It went back to the dealership, who took it for a test drive, was unable to replicate the issue, checked for twisted lines (none found), updated the TCM, and noticed the transmission was down 1L of fluid and gave it back to me saying it's good to go. While I doubt this is fixed, I will take my trailer for a drive this weekend, but fully expect it to overheat again. 1L on a 11-12liter capacity 10L80 would not cause the transmission to go nuclear this quickly. I'm guessing there's either a blockage, or the bypass valve internally is faulty. As far as the GM post above, they emailed me back and supposedly are acting as a mediator between the dealership and myself. We'll see if it goes anywhere, but as of yet I haven't heard from anyone.

Yes I did. Good thought though!

I'm thinking taking it to another dealer in another city is my only option. Does anyone have a similar built truck that could share their normal operating temperatures?

Hey all, Looking for some input on my truck. It's a 2022 Sierra 5.3 with the 10 speed transmission. It has about 3000KM (around 2000 miles) on it. When I was towing my trailer the other weekend (about 5000lbs) the transmission got to 257F (125C) within about an hour of towing. I pulled over to let the transmission cool, because it continuously was rising. I was not working the truck very hard at all, allowing it to slow on the hills, etc. The ambient temperature was about 80F. I took it to the dealer, and they told me this is completely normal for these trucks, and that it didn't set a code. I got them to put it in writing, but I really don't want to cause additional damage. I've never owned a truck that allowed the transmission to get this hot. Is there anyone that has some specific information on this? I read the TSB about the twisted cooler line, but my dealer didn't even consider it an option. Would love some help with this or at least some comparisons in terms of transmission temperatures, options, etc. Arthur