Wxman

With the factory GAS setup the two batteries are only connected with ignition in 'run' position. This allows charging of aux battery by alternator. In other ignition positions the two batteries are isolated. This protects starting battery from discharge when using aux battery for camper, accessories etc. With ignition off, charging either battery alone will not charge the other battery. I use a two bank NOCO Genius during extended garage times. Cheers

Have you experimented with the Tow/Haul mode? I think it is supposed to boost charging voltages. Don't know about the idle/park/neutral stuff.

Allycat75 Two things. One I agree with CamGTP that you aren't likely hurting the trans in that situation. I have even read the transmission can take temps up to 260, but I too would be concerned about the fluid at that temp. Two, has your truck have the cooler transmission thermostat installed? It won't keep it cooler when it is maxed out, but if you start a little cooler it takes that much longer to get to temps that are worrisome. You can visually tell if you have the cooler thermostat or not. I had TSB 21-NA-199 1..3 (nhtsa.gov) accomplished on my 2020. Later builds had the cooler thermostat from factory.

Yeah thanks. I have used some 'dry lube' a couple of times (trying to avoid collecting dust). Maybe I will have to break down and go with some silicone. It works more than it doesn't but not dependable. I have to use every time I park in my garage.

Well, went from dying to dead pretty quickly. Can't find anything about replacement 'guts' so I guess I am ordering a new one. 11 days out of warranty.

Hello all Any aftermarket 'guts' available or recommended for the mirrors, gears/motor? Might have one dying and would fix myself if possible instead of going with OEM replacement. Thanks

As to OPs original question. I have been running 58 ft / 55 rr in my 2500 for 25000 miles. Air them up to 60 and 70 when towing the RV. No unusual wear. Do get the occasional TPMS warning on the rear on cold mornings etc. I have the 20 wheels and the OEM Goodyear Trailrunners. Happy trucking!

I have also installed the B4600s. Certainly noticed less 'movement' both loaded and empty. I much prefer the ride over the stock shocks. Huge difference when towing the RV.

Will this help? Power Distribution 1.pdf

I had similar issue. Passenger side mirror got noticeably slower to retract/extend relative to driver side. Eventually it didn't retract on its own. I extended and retracted again and it would work. That happened two or three times before it finally refused to move at all. I have to retract to get in my garage. The second time I manually extended, after manually retracting to get in garage, I had done the manual extension before I used the button to extend the driver mirror. When I extended the driver mirror the passenger mirror made a huge pop, really huge pop. It has been working perfectly ever since. The speed matches the driver side and everything. It has been months since that has happened. No idea what was happening or how it fixed itself, but it did.

Will this help? 12 V outlet description.pdf

Some good options above. I don't think all of those were available two years ago. I installed the larger GM flaps right after purchase and quickly decided they didn't give the coverage I wanted. My hack solution in pics. They keep stuff off the truck.

Yes, newdude's info agreed with what my dealer parts/service people told me. They also told me that if I had them do it they normally used the 75w90 in both front and rear. I bought and used the 75w85 front and 75w90 rear. Almost free using the reward points from truck purchase.

2021 with about 13000 miles. Yes, I have had this happen, although rather infrequently. Probably more like a second than two or three for me. I recently drove an F450 uhaul, did something very similar but worse (really lurched when it 'caught'). Just had trans serviced when dealer did Thermal Bypass TSB. Not expecting any change, but everything looked when in the shop. I haven't been too concerned yet. Good luck

Just a follow up to close this out. I ended up having dealer do the TSB and went ahead with a fluid/filter change as well. Always like to do the first one early anyway. Dealer had no problem doing the TSB - (After I showed them a printout and a little discussion with the advisor.) Ordered the parts ahead of time so they would be ready for the appointment. Looks like the work went well, new valve has the '70'. It was the 85547828 part number. Temp looks like it is running 25-30 degrees cooler running around empty, 150-155 ish vs 180 ish. Haven't towed yet to see if it runs cooler under load as well. Happy with all that even though appointment was a nightmare. Appointment to drop off on Tues. Dropped off at 0715. Called at 1600 to check as my ride needed to leave. Hadn't been looked at yet. "Hopefully in the morning". Got a call about 1400 Wed, "You are next in line, but I didn't realize it was a Duramax when we checked it in." ?????Convinced advisor it was gas and they could proceed.???? Still didn't make the cut to get worked on Wed. Finally at lunch time Thurs the work was completed. And they wonder why I don't let them do oil changes, etc. Ridiculous! Happens I was working at home this week and I wanted this work complete before leaving on a camping trip Fri. Still, probably won't be darkening their service door again.

Got it now, thanks. Finally found a copy of the Dec TSB with all part numbers. GM Parts Direct was apparently incorrect when they told me the 7828 valve would be the same as original for my VIN. That doesn't agree with TSB and my valve does not have any '70' markings. Thanks all.

Hey all. Based on my VIN gmparts direct suggests 85547828 instead of 86774933. I am asking them to confirm the '828' part is 158F valve. Anyone have insight on this? Local dealer was blank stares when I started asking questions about the TSB and TBV temp change. Thanks

Thanks. Didn't make that cut. Maybe I can get dealer to do the 'upgrade' and change the fluid/filter with supplies I already purchased in anticipation of doing it myself. Always liked to do the first one early and get all the break in material cleaned out. Thanks again for the info.

So this bulletin applies to the 6L90 in the HDs as well? I couldn't find info confirming this, only the 6l80. I have a March 21 2500HD and the trans seems to settle in the 190s most of the time. I do spend almost 50% of my miles towing 10k travel trailer. Want to save the tranny. Where can I find this valve to look for the "70" stamp? Thanks all

I am no pro but for FWIW I always thought indentations were OK (cosmetic manufacturing issue) and outward bulges were bad. I have never had a 'bulge' shaped like those in your picture. I have had several tires replaced (low profile car tires) with sidewall bulges although the bulges were more round or oval than in your picture. (Finally got rid of those tires :)) They were not much bigger though. The replacements were through Discount Tire and their cert program. Maybe run by a dedicated tire shop and see what they say. I THOUGHT the tires are a separate manufacturer warranty anyway and an authorized tire shop could take care of replacement. But I am not a pro Good luck

Glad a fuse solved part of the problem. I had the exact same symptoms as your #2 description. Two different trucks with previous trailer. Problem would be nearly constant back and forth one day and then fine the next. Intermittent nature made troubleshooting a nightmare. I was led down the path of trailer plug, truck plug, umbilical cord, ..... Often I thought it was fixed (intermittent) and then the messages come back. Finally found a shorted wire inside the axle tube (lamp cord kinked) where the brake wires were run from driver side to passenger side. Fixing that really fixed it. That shorted wire was completely burnt in two. Best I could tell in the end, when it would bounce around and short against the axle I would get the Check message and brakes inop. Really bad part was at the end I don't think I had brakes on passenger side even when Connected message was displayed and controller worked. The wire would bounce around and no longer be shorted against axle so Check message would go away, but by the time I discovered it the wire was certainly not sending any current to passenger side brakes. In the beginning of troubleshooting I had checked and did have brakes all around during Connected message. Evidently the short eventually burned through the wire and I falsely assumed Connected meant everything working and Check meant nothing working. Long post I know. I fought with this for 2.5 camping seasons. Wish you better luck than I had.

I found a lot of electrical schematics at GM upfitter dot com when I had questions. good luck

Any resolution to this problem? Sure it didn't cause an actual problem with the trailer brakes? (loosened magnet, connection, pinched wire, etc...) I guess I would have started with trailer with that message.

2500 here (60/70 on the door). I have been running 58 front and 55 rear when empty. No lights. Tires look great >10k miles. I air rears up to 70 when towing my travel trailer. I really don't ever carry a significant load. I do have the 20" wheels and Trailrunner tires.

Sierra 2500 SLT. 4WD, Driver Conv 1, assist step, skid plates, aux battery, 20 inch wheels. No sunroof or 5th wheel. 3385 for the payload.