ArthurW

Just as a final update to this for closure for anyone who's interested; I traded the truck in and I now own a 2026 Ram 2500. Due to the horrific support (or lack thereof) from GM, I've opted to leave the GM family, and won't be back until they figure out a process to help in situations like this. Through two different dealers, dozens of emails back and fourth with GM Canada Support, constant lies, 12 visits to dealerships, and not a more than 1 single fix was found (or even attempted) for my truck. I've been a GM fanboy for as long as I can remember, and unfortunately due to the current state of their affairs, there's absolutely no way I can support this company any longer. Best of luck to anyone else who has problems with their 10 speeds, this was a disastrous experience for me, and I'm glad to be done with it.

Hi. - I was running about 55-62MPH (90-100KMH) - Steady-ish speed, I let it slow down on hills (fairly flat province though, we're talking small grades, not mountains or anything like that). - I don't really run much highway, most of my drive time without the trailer is approximately a 15-20 minute trip to/from work. Each way I normally hit anywhere from 180-200F during the summer. In the winter it's cooler, as right now it's pretty cold here. I haven't looked at the temperature recently, as usually in the winter I'm not towing nor do I notice any temperature problems. - Camper is a older Prowler 25LX which has a base weight of about 4500-5000lbs. I don't haul it with the tanks full, ever, and our gear in the camper is fairly minimal, but probably an extra 500-1000lbs to be safe. It's 25ft long, typical camper trailer. No slides or anything like that. Truck doesn't struggle much at all power-wise towing it (well it does compared to my old Duramax, but not the same animal lol) and I don't push the truck hard. I'm never in a rush. - EDIT: Also for reference, it also runs pretty stinkin' hot just hauling my utility trailer around with a couple walk behind mowers on it. Probably 3000lbs gross. Just toodlin' around the city I'll easily see transmission temperatures of 240+. EDIT 2: I should also mention, I'm from a rural area in Canada. When I say "city" we're talking a population of 70,000 or so. No traffic, or anything like that. Just slower speeds.

Hi Jason! Absolutely not - I've not received any help, nor have I resolved this issue. I'd love to speak to someone who has some experience with this transmission to help out, or at least give me some ideas. Anything you can provide would be a great benefit to me! Thanks, Arthur

Yeah that was with the transmission over 100c I believe. I have a video showing all the temps, pan was like 119 I think, lines near pan were 90s, and lines near cooler were 30 and 20

I have some videos of the same process, both in front of the truck at the cooler and also underneath. Been down this road unfortunately.

Unfortunately it is part of the valve body on the 10 speeds with the gas application. Probably explains the reluctance on GM's part to do anything to help me. I have very similar symptoms to what you had though. Temperature just continuously goes up, never comes down. I've basically given up on it at this point. After 12 visits to the dealer, countless headaches, phone calls with GM Support Canada, and countless emails, a meeting with the general manager of my local dealer, a meeting with a service manager at another dealer, I have literally gotten NOWHERE. I really like GM's trucks otherwise, but the dealers around me aren't willing to do anything to help me. I've just come to the conclusion that I will trade the truck in when it makes sense financially, and never come back to GM again because of this whole ordeal. I don't even care that the truck has issues, the problem I have is that it's been a ridiculous headache trying to get some layer of service to help me with the issue. I won't buy another GM. From my experience where I live, and with the lack of support on my local dealer's, and GM Canada's part there is no way I can risk having to go through this again with another vehicle. It is what it is, but it's a shame that someone who's been an avid GM guy for years has just been let down this heavily. This issue will affect my families purchases, and most of my social and professional work environments purchases moving forward who all know about the issues I've had. All over a call it maximum $5000.00 repair.

Little delayed in getting back to you - but thank you for the information. I will double check this next time I have the truck hot. For reference - it would be fairly easy for me to overheat my transmission if I was to "drag race" my truck while towing. I watch these videos of people towing, putting the pedal to the floor while climbing a mountain to see how it holds speed, etc. My truck's transmission would overheat in 10 minutes if I did that lol. I have a shutter now while driving at highway speeds, (kind of intermittently) and a few real weird shifts/flares at times. Unfortunately all of these issues are very intermittent, and I know my dealer would "not able to replicate" it lol.

Is there any technicians on here? I'm trying to figure out if the thermal bypass valve is something that can be replaced in the valvebody on the transmission (10l80). I know on the 10r80 you can, but curious about GM's.

I haven't, but if he was to rectify this issue with me I'd likely rescind some of my words and anti-recommendations from them. I have some buying power influence at my employer and I can assure you there is a reason our last two service vehicles were Fords lol.

And another update - spoke with the General Manager from the local dealership, he's going to look into things. I'm not super optimistic, but let's hope.

Putting it in perspective, I spent an hour on the phone with GM Support who could help me "find a dealer", and then after quite a bit of discussion "maybe" get me a managerial discount to buy a new truck. That said, I would still lose 10K on the deal likely because of the fact that I've only owned the truck for about 9 months now. Man, General Motors really has really dropped the ball on this one. Shame. I'll update as I continue with this process.

As an update - the second dealer has opted to not touch the truck as they don't have a transmission technician. I guess I'll have to try another dealer. GM support hasn't really been all that helpful with getting an answer.

Really depends on the length of drive, the longer I drive the hotter it gets, but the rate of increase is a lot slower when I'm not hauling VS when I'm hauling. It just never cools (no fluid coming to the cooler by the looks of things), and just continuously raises the longer I drive/haul. Generally, probably anywhere from 160-190F just normal driving. I've actually never had this truck on a multi-hour road trip, so I have no idea how hot it'd get just cruising down the highway for an extended period of time. The longest I usually drive uninterrupted in this truck is probably an hour or so down the road (and even then, that is only once in a while) most times its 15-20 minute trips.

Thank you for this, anything helps! Is yours a 5.3 with 10 speed as well? Mine would've gone well above 162 in 30 miles lol

I may be mistaken, but I believe the bypass is part of the valve body on the 5.3 variation of the 10 speed. Also - follow up question: does anyone notice a whining or whirring sound coming from the transmission? My best explanation is the kind of sound a bad idler pulley would make where it's a grindy/growly/whine. (Mostly whine) It's not super loud, but I can hear it at idle and light throttle when in park/drive, etc. I can't hear it as much on the road but that's likely because the road noise covers it up. I have heard it could be normal, or maybe not. I think a guy at work has a 24 5.3 with the 10 so I may see if I can take his for a run to compare.

Exactly my thoughts. After hauling the camper yesterday, transmission was up to 120C after about an hour (around 250F). I checked the cooler lines up front with an infrared and they were at 30C (around 85f) so I think that should be adequate evidence to help the technicians to diagnose and fix this. I have pictures and videos to show them, pray that they listen to me lol. I also have clunking in the rear end which I assume is something to do with the Leafs that it absolutely driving me crazy so hopefully they can deal with that too. I told the other dealership about it last year as well and they told me they couldn't recreate it. My blood boils just thinking about their incompetence lol. Pray for me al! Hope that this is resolved soon(ish).

I don't have a lot of choice at this point, I'm being stone-walled by my local dealer and "GM Support Canada" is about as useless as can be. With this other dealer about 45 minutes away (one way) it's a royal pain to have any kind of service done because I need to have my wife pick me up. That said, I'm going camping this weekend so I expect the truck to go nuclear again and see if they can help me this time. It does not have that package, no. I agree. If you can get me any of those temperatures I'd be super thankful, maybe something to beat the dealer with over the head. I'll know a little more today as I'm towing my camper about 100ish KM (65ish miles) and I fully expect it to get up to 120C+ (250+F). I'll check cooler lines when I arrive or on side of the highway if it overheats. @GMCustomerService

Today after towing my landscape trailer around for a while came home with the transmission around 105C (220ish F) and I took a heat gun and checked the temps at both transmission cooler lines (at the cooler, one on each side), both were about 35C (about 95F) I'm thinking they should be a similar temperature to the actual transmission temperature. The bottom of the transmission pan was about 90C (averaged out, some spots were over 100, some were around 80) and the cooler lines close to the transmission were about 70C. Can anyone who is has a infrared gun check the temperature of the lines going out of both sides of the transmission cooler when they get back from a drive where the vehicle gets up to normal operating temperature?

No they haven't yet, one dealer claimed to replace the shutters, but had no effect. It's starting to shift strange too at times. Kinda "mushy" if that makes any sense. I believe this will be my 10th visit for the same issue with zero fixes lol. The other day I hauled a little tractor (about 3000lbs) about 25KM (15 miles) and the transmission was at 100C (212F) by the time I got home. Usually with just normal driving I'd probably say in the range of 155-195. I normally only drive to and from work (about 20km (13 miles)) and it's usually about 65-70C (158F) when I get there. (Driving in temperatures around 5-10C (40-50F). Tomorrow I'll actually watch it a little better, it's still pretty cool up in my part of Canada so it takes a little longer for it to heat up it seems. I'll report back tomorrow driving to and from work.

Just as an update - still an ongoing issue. Loaded trailer yesterday with some gravel (4500lbs worth) and within 20 minutes (14 miles) of driving back home from the pit my transmission temperature went from 50C (122F) to 110C (230F). (Only reason it stopped going up was because I got to my destination) So I'm certain once again it's a lemon, back to the dealer I go.

Hi, sorry for not checking in. The other dealer replaced the shutters, but I haven't noticed any noticeable difference yet. It's been consistently -5 and colder (20s in f and colder) and I haven't towed anything so I haven't had an overheat condition since. I have noticed a few rough shifts here and there, and a little bit of a 'hum' coming from the truck in the last few weeks but I credited that to it being cold outside. Transmission temperature wise it's still been floating in the 150-170 range, but I haven't really worked the truck. Sadly I probably really won't know if it's fixed until I have the opportunity to tow again. This new dealership seems a lot better to deal with, but I really do still think I have something going on with the truck but I'm not going to burden them with fixes unless I can reproduce the problem.

Exactly my thoughts. I've never experienced temperatures like the ones that my truck currently regularly hits. I understood that these trucks ran a little warmer than my old gear to increase efficiency, but it seems to me that mine is obviously well outside of specification. I would imagine on most trucks that have a fully functioning transmission/cooler it would take some serious effort to get the transmission to overheat fully like mine has. I remember towing multiple loads on previous trucks that were outside of their specifications/limits, but my transmission never got anywhere near where my current Sierra is getting while pulling 50% of its rated capacity.

yeah the only rationale I could come up with is that my truck always runs hot (transmission wise) like the transmission temperature on the way home today from the dealer was around 165F with an outside temperature of 32F but it becomes excessively bad when I'm putting load on the transmission like towing. I do have a bi-directional scanner, I may go out this evening and play with it and see if I can see any codes/control shutters.

Yes, as in it hasn't fully overheated. But it generally runs hot most of the time while towing, very rarely have I ever seen the temperature go down as opposed to constantly raising. It just depends on how long the drive is, sometimes it only makes it up to 240F and other times it goes all the way to 270 and causes the alarm to go off.