EXSlider400

I use Fluid Film and in black…but try sell clear as well. https://www.amazon.com/Fluid-F80-AS11B-11-75-Aerosol-Lubricant/dp/B08WRMLPCG/ref=sspa_mw_detail_multi_sbb_img_m_sccl_1_1/138-9516956-0122857?pd_rd_w=suZLb&content-id=amzn1.sym.d42cefb2-fcdb-4dd6-bbdf-2aa4ef1ab24f&pf_rd_p=d42cefb2-fcdb-4dd6-bbdf-2aa4ef1ab24f&pf_rd_r=JC8NQXDP0QBKME212GAC&pd_rd_wg=oFxxi&pd_rd_r=13c75b1a-212d-4837-9f4f-12a533613cfd&pd_rd_i=B08WRMLPCG&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWxfdGhlbWF0aWM=

With all the electrical on new trucks, I recommend adding an additional grounding strap. This may help;

This is what worked for me.

Yeah, my power steering flow sounds like it has air or rocks in it from day one… any pressure on the steering wheel in either direction it hisses and bubbles…sounds like this L8T is an L5P. I need to bring it to the dealer before the warranty runs out. From reading other responses though I’m afraid that’s just normal…. I guess the other option would just be to go test drive a comparable truck and see if it makes the same noise… but that still doesn’t fix it. I assume it is like others have said and related to the digital steering assist (RPO code NV8). Did find this though: https://static.nhtsa.gov/odi/tsbs/2025/MC-11013018-0001.pdf

This would also be my suggestion. I had the previous generation L5P and if I was making a lot of short trips, taking a good long road trip always seemed to help the regen do its thing. Also make sure you’re using good DEF….(not old stock as it degrades quickly) If you’re getting it out of a box/container, check the date (there’s a way to decipher the printed code on the box …just google it.). If you’re just pumping it in, make sure it’s a good high-use busy station.

These trucks don’t really “coast“ very well. Understandably why and look I tow with my truck, but when I’m not towing some sort of economy mode, which allowed for more coasting would be nice (if it’s possible which I am not sure if it is). Anyway, so going downhill or letting go of the throttle really doesn’t help that much. I feel like I need a clutch, but these 10 speeds are so complicated, I’m surely not putting it in neutral when in motion. There’s a spot on the Natchez trace Parkway where I get really good gas mileage, but I’m going 54 miles an hour I might try doing speed limit, which is 50 and see if I can get a little better. I’m going on the interstate if I keep it under 70, I can get around 19. But I also have a an aggressive all-terrain Goodyear Wrangler Dura-trac RT in the factory 275/65/20 size but they’re still very heavy at 63 pounds each. 25 mile average 50 mile average

Ok found the part number that should work. 12691785, which replaces part number 12670017… but unsure if it will contact that small rubber upper manifold hose… Here is a shorter one…but GM has many. 12609623 here is a Dorman that Autozone and O’Reillys carry

I have used Lucas bottles as an oil funnel for decades… this truck needs that angled piece and as soon as we figure out the part number then I will get it… but in the meantime I noticed the bracket for the second battery was hitting the oil jug… so I slightly bent it out the way and then cut a Lucas oil bottle like this to fit the angle of the valve cover and prevent spills. use a Fram Endurance (same as Amsoil) and a magnetic plug

Thanks. That is great information.

Has anyone swapped their fender, flares for the wider ones that come with the AT4X? It looks like it would require not only the flares, but the end caps as well? I think these are the GM part numbers (showing most current not the ones it replaces). Front Left: 86507835 Front Right: 86507836 Rear Left: 84660041 Rear Right: 85044876

When I go to car shows, you would be surprised how many young kids ask how to roll down the windows because there are no buttons…and I still love my side vent windows. BTW… Cruisin the Coast is right around the corner!!!

But this is the only vehicle I have driven that the fan speed does not return to the higher speed after the call ends. Gets annoying to keep turning it back up after every call or text.

That one had me hopeful but dang no luck.

I’ve had the same phone for about four years and it is an iPhone 11 I think but either way it only does it in my new truck, when I travel for work it works in all the rental vehicles, and this same phone worked fine in my old 2019 sierra. I had not updated it since it worked in my old vehicle so nothing had changed, but I did update it tonight to the new iOS, but it still doesn’t work. Tried it with my wife’s phone as she has a brand new iPhone and it still doesn’t make the fan speed go back to normal after a call either. Appreciate the good idea though.

Excellent job I’d much rather use factory parts. This is the next thing on my list. Let us know if you notice any MPG or other changes. Thanks again.

Yes, this is definitely being nitpicking… but want to just ask if anyone else noticed this. When a phone call starts over Apple CarPlay, it lowers the climate control fan speed, but on every other vehicle I’ve driven (I travel for work so trust me I’ve driven a lot of rentals), including all my other GM vehicles, when I’m done with a phone call using Apple CarPlay the fan speed automatically reverts back to what it was previously set to. But this vehicle (2025 HD SLT) I have to continuously put the fan speed back manually once the phone call has ended. I assume this is a programming error that can be fixed via over the air update.

Just saw this today related to the 2024-2025 issues: https://youtu.be/rU8_hyuIVzI?si=ByP-c-GMj1pIYFHo

Love the color. I see you changed the front bow tie to black… looks much better with all the other blacked out emblems. A black tip would also be nice. This is the one I used and so far works great.

Sorry to hear that. I also just purchased same Truck about a month ago. I followed the break-in instructions even a little longer than GM said to. I knew about the valve body issues on the 2020-2023 but supposedly GM fixed the issues with the gen 3 valve bodies that have more wear resistant castings and hardened feed limit valves. But, your post is not the first that I’ve read about the new transmission is still having issues… that gets me worried and I wish they would also extend our warranties like they did the ones covered under the recall/special coverage N242454440 and N242454441 (honestly if a heavy duty truck can’t make it to 150,000 miles under heavy duty use then it shouldn’t be allowed to have an HD designation…). My 2007 4.8 1500 had almost 400,000 miles on it before it finally just gave up and besides following a good fluid change interval, the only thing that required replacing where wear items). These are two links for good information about the updated gen 3 valve bodies. https://tieronetransmissions.com/20-25-duramax-10l1000-valve-bodies#:~:text=These new Generation 3 valve,of a reliable valve body. and https://nextgendiesel.com/products/project-carbon®-10l80-e-diy-valve-body-upgrade-kit-v3-1?variant=44018016157869

The Ultimate grill may not match the SLT bumper. Black chrome vs chrome. I deliberately went from an AT4 to an SLT because the black chrome is just a tinted clear coat over the chrome and after a few years mine looked horrible (but that depends on individual driving environments and conditions and some say the newer chrome may not hold up either). My 2 cents for what it is worth.

I don’t think it’s supposed to have a nut. Mine does not have one there either. I’m thinking the noise is heat is just power steering pump and fluid flow…. only because my last vehicle was a 1500 with electric steering.

Is this still an issue with 2025 trucks? I assume so and if that is the case then I will have to do the fix in the future for my new 2500 (traded in the 2019 1500).

https://www.gm-trucks.com/forums/topic/255000-diy-sliding-window-leak-permanent-repair/#google_vignette I did the repair above to a 2019 1500 and it lasted, but just got a 2025 2500… is this still an issue with the new trucks…I assume yes.

Brand new 2500 gasser and when I drove it home from the dealer it was raining so did not notice it but mine rattles and I noticed the noise occurs when any pressure is applied to the steering wheel when at idle or any increase in any RPM. Could it be the hydraulic power steering? Sounds like a faint diesel clatter.

This may seem crazy, but has anyone rerouted the exhaust crossover away from the pan? I was thinking about doing this on 2025 2500. I did the exhaust disconnect on a 2019 6.2 with 10-speed with over 100k miles and it was a pain and assume the 2500 will be very similar.