10 speed Transmission Hot - Please help

TrueBlue · December 23, 2023

I too would expect that the tranny coolant lines would be all metal. So the picture is confusing from that standpoint alone.

mjm-1957 · December 23, 2023

They are hard lines from trans to about the front of the engine then have crimped rubber sections to allow all the bends necessary to go to the cooler fittings.Those trucks are murder to do anything on. Can barely see them from the top of engine compartment.You should see what we go threw to change an engine in one of these .

ArthurW · December 23, 2023

39 minutes ago, mjm-1957 said:

hard lines from trans to about the front of the engine then have crimped rubber sections to allow all the bends necessary to go to the cooler fittings.Those trucks are murder to

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

gemarsh · December 23, 2023

After all this, I'd be pi$$ed enough to load it up to gvwr and smoke the tranny.

ArthurW · January 3

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).

Quote

Hello Arthur,

Thank you for your patience while we reviewed the transmission events you brought to our attention. I reviewed the details with my team as well as the Service Manager Shawn at (REDACTED)GMC and we have taken the following information into consideration. Your vehicle is within New Vehicle Warranty by time and kilometers; this warranty expires on July 31, 2026 or 60,025 kilometers. Your vehicle is also within Powertrain warranty which ends July 31st, 2028 or 100, 025 kilometers. We confirmed during the diagnosis that no codes were found and it is advised to not replace parts at this time. Based on the information provided, we have come to a mutual decision that no fault has been found. We ask that you monitor when the concern arises and to return to the dealer so it can be identified as soon as possible. In the meantime, I am happy to connect with you within a week from now to understand if your Sierra is presenting any signs previously experienced.

Regards,

Davenielle

GMC Canada Care Ambassador

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.

Edited January 3 by ArthurW

brianf60 · January 4

I feel for you. I have had similar results with the 2 new vehicles I bought in the summer. My Trailboss required 5 trips to the dealer and over 3,000 km to get a defective tire replaced on a brand new truck. The first visit was within 12 hours of purchase and the agreed it had a really bad vibration but told me they couldn’t balance the tires until it was driven at least 1,000 km. I lost so much time and money on fuel driving there I should have bought new tires myself.

my wife’s Tahoe has been to the dealer 4 times for a seat rattle. Nothing has been resolved.

Since august we have made 12 visits to the service department. We spent close $200,000 buying these 2 vehicles but can’t get any of the defects resolved in a timely manner. I have anxiety worrying about how it would go if we had a real problem. If they can’t fix a tire shake or a seat rattle there is no way I can be confident in them fixing a complex issue like yours.

ArthurW · January 4

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.

TrueBlue · January 4

Strange that the other dealer could not see the code. Also that they would not have this potential cause on a list of things to check for.

I'll be very interested in hearing your outcome. Did this new dealer specifically say that closed shutters could affect tranny fluid temps?

Also, did you find that your line is not twisted or kinked as that TSB described?

Good luck, and I hope very much that this fixes the issue!

ArthurW · January 4

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.)

TrueBlue · January 4

Sounds promising. Not just the potential issue but also the dealer who is looking beyond what they already know (or don't). Good luck!

Oh, and one other question, the answer to which you might want to pass along to them. Has your truck ever towed anything without overheating?

Edited January 4 by TrueBlue

ArthurW · January 4

26 minutes ago, TrueBlue said:

Sounds promising. Not just the potential issue but also the dealer who is looking beyond what they already know (or don't). Good luck!

Oh, and one other question, the answer to which you might want to pass along to them. Has your truck ever towed anything without overheating?

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.

TrueBlue · January 4

The reason I ask is that if it gets hot every time you tow, but not every time otherwise then if your issue does have to do with the shutters there must be something about towing that is triggering yours to stay closed under load. Makes me want to hook up my big trailer to make sure I don't have the same issue. Will wait for Summer for that though.

I have seen youtube videos (maybe linked in this thread?), that show how to remove every other set of fins in the shutter housing in such a way that it always allows airflow, but doesn't trigger a CEL as it would if you removed the whole assembly, or otherwise stopped them from operating altogether.

Oh, and if you have an OBD2 scanner, have you ever checked for a code yourself, with no light actually being on?

ArthurW · January 4

21 minutes ago, TrueBlue said:

The reason I ask is that if it gets hot every time you tow, but not every time otherwise then if your issue does have to do with the shutters there must be something about towing that is triggering yours to stay closed under load. Makes me want to hook up my big trailer to make sure I don't have the same issue. Will wait for Summer for that though.

I have seen youtube videos (maybe linked in this thread?), that show how to remove every other set of fins in the shutter housing in such a way that it always allows airflow, but doesn't trigger a CEL as it would if you removed the whole assembly, or otherwise stopped them from operating altogether.

Oh, and if you have an OBD2 scanner, have you ever checked for a code yourself, with no light actually being on?

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.

TrueBlue · January 4

Mine is only an LT, not an HD, and I've yet to pull either of my trailers with it yet, but last summer in the worst of our heat (90+), if memory serves it never got up to 165. Most of the time it ran around 145 or so. But even towing, since these trucks are engineered to haul relatively large loads I can't see where they would be designed to "normally" run in the temps you've reported consistently. Especially with cast aluminum engines and trannies. Then again I'm not an engineer. But I have been driving cars and trucks for more than 50 years. Your situation is well outside of any experience I've encountered.

ArthurW · January 5

6 hours ago, TrueBlue said:

Mine is only an LT, not an HD, and I've yet to pull either of my trailers with it yet, but last summer in the worst of our heat (90+), if memory serves it never got up to 165. Most of the time it ran around 145 or so. But even towing, since these trucks are engineered to haul relatively large loads I can't see where they would be designed to "normally" run in the temps you've reported consistently. Especially with cast aluminum engines and trannies. Then again I'm not an engineer. But I have been driving cars and trucks for more than 50 years. Your situation is well outside of any experience I've encountered.

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.