UWSkier

Finally got into a dealership to have the shift relearn done and it's back to shifting smoothly. It took 11k miles before it started acting up before. Hope it's good for at least a few thousand miles of towing before it hits again. Really sucks not having 8th gear on a cross country tow.

I saw 212F in the climbs towing my 8000ish lb travel trailer through Arizona last week. Gasser so it was turning a few revs, between 3200 and 4000 RPM pulls.

it's kindof crazy they've opened this in March and had no updates though. It's pretty annoying when it happens towing. It sounds like the truck is going to spit the whole driveline on the highway, and that's a gasser towing a travel trailer. I have to imagine it sounds like the rapture itself if you're running a Duramax and a 25k lb toy hauler. I've basically just had to drive it with anything above 7th gear locked out. My truck shifts 7-8-7-8-7-8 a lot when towing my camper 70-75 MPH. It'd be banging every 5 minutes or less.

Thanks! I may call a local dealer at my destination to see if they can at least get me reset so my wife doesn't think the truck is falling apart every time it shifts. LOL

I've been told that I should try to reset the TCM by disconnecting the battery for a half hour. Paging @newdude since he knows more about this stuff than just about anyone... would this work? Or do I need a dealer handheld to force a fast learn... and is it even worth trying? Still just that one gear change after 1200 miles towing.

Not sure if TX has a lemon law, but it sure seems like yours is cursed...

Did the hard hot climbs today and trans never got above 212F, which was good. Shifting from 1-7 is buttery smooth. What ISN'T at all good is the 7-8 upshift. It's a clunk every time unless I'm coasting. I've locked out 8th gear for the drive and only manually kick up to 8th when I'm on a flat or downhill section for a bit better fuel economy. Truck has under 11k miles on it. NOT happy... How does this transmission hold up to a Duramax if a 6.6L gasser is too much for it?

so I've noticed that if I manually cycle through the gears, this NEVER happens. Every shift is butter smooth. My truck has exclusively been a tow vehicle for my boat for the past 500 miles or so, and I like how it drives better with tow-haul disabled for my 3500 lb ski boat. I'm thinking perhaps the transmission has learned that there's typically a load and has stiffened up that 8-9 shift point accordingly, which I feel unloaded. About to head cross country with the RV and I will definitely be using tow-haul for that. Will be pulling some 7% grades at 115F or hotter ambient. Will see how hot the transmission gets on those stretches.

I noticed yesterday when it was 110f out and my truck was hot, if I'd shut it off, then restart it, it'd only make the noise for a few seconds right after starting... maybe...

Went cross country towing the camper in my seats when new (500ish miles). Ran ventilation on high the whole way. Didn't have much problem with them being too firm, but they are firm as heck. I'm 6'5" 255 and they work OK for me. My 5' 100 lb wife OTOH, she sits on one of those gel butt pads. Wife has a Mercedes EQE. Wish I could transplant those seats into my HD. About to go cross-country again...

Weird... harmonic vibration in the bendix maybe? Looking forward to the report back! Tempted to throw mine up on the ramps and put my mechanic's stethoscope on the starter.

You're probably better off building some sort of pad for the wall and let the truck come to rest against it. I do the tennis ball trick also and find that if I'm backing in and shift to P once I touch the ball with the rear glass, the truck will still roll back a couple inches as the slack comes out of the driveline. I suppose I could trigger the parking brake whenever I park, but that's kindof annoying.

I don't think it's belt related given it goes away under engine load and at higher RPMs. I'm thinking it's: Exhaust leak from a flange somewhere Valvetrain noise Injector noise

Does the HD transmission skip shift? It seems like I can watch my tach and count the steps up into higher and higher gear. I'll listen for the whine. This truck makes so many funky noises, it's hard to keep track of them all.

shifting up. Happens mostly when accelerating lightly to moderately as it shifts up through the remaining gears once the rate of acceleration is tapering off. I've noticed the occasional clunky downshift coasting or braking to a stop, but less obvious.

Did you guys notice any erratic or harsh shifting before things went south? I have a gasser with random hard shifts. 95% of the shifts are silky smooth, but occasionally, it's a kick in the behind.

EDIT: I can for sure say the problem is upshifting from 7th to 8th gear now. If I'm on the power at all for that shift, there's a clunk. Every time. If I'm coasting, no clunk. Shifts below 8 and above 8 are fine. Just going from 7 to 8 is no good. __________original post below_____________ Truck has 10,500 on it and the transmission has been a non-issue until just recently. Occasionally, when accelerating with part throttle, say coming up to 50 MPH or so gradually, I'll get a rough shift. It doesn't seem to do it if I'm on the gas hard, and it doesn't happen every time. Anyone else seen this on their 2024? Do I just need to take it out and flog it a bit, or do I need to drive like I have a raw egg under the pedal? I'm about to leave on a cross-country trip towing the camper so this is super great timing with the current cyber attack crippling the auto dealers (scheduler I talked to today said he wasn't sure when they could even begin a diagnosis).

autonation, Gilbert AZ

dealer pinged me and said I'd need to leave the truck for 25 days before they could look at it... looking for different dealership, so no, haven't had it in.

Strangely, when new, I would get the fast flash 5 or 6 times on occasion. It hasn't happened in probably the last 10 months or so.

It goes in on Thursday unless something comes up.

Not on a truck camper, but I love my Haloview system for my travel trailer. No reason it wouldn't work on a truck camper also.

Receiver is there. Behind a signal deflector/license plate. Will try them without relocating, but see that some have moved the sensor to a more reasonable location with a simple bracket.

One thing I wish my truck came with, which it did not, is TPMS sensors for the trailer from the factory. I've read that the receiver is on these trucks by default and that the sensors can be added later. In poking around on Ebay, I see a few different GM part numbers that all say they work with 2024s, but I know the 2024s have different TPMS, at least on the truck, than prior years. Does anyone happen to have one of these 2024 sensors they got with their truck laying around that they can grab the P/N from by chance? It's time to put new tires on the camper, and I'd love to use the integrated TPMS, instead of the TyMate I've been using (which has been solid with the repeater antenna BTW).

I reprogrammed my tpms so I can run 50 PSI in front and 45 PSI in back and the ride is WAY better. Still don't like the lack of rebound damping in the Ranchos, but the square edged road junk and potholes are much better with these pressures, and I'm getting nice even contact across the entire tire now instead of just riding on the center ribs.