Another JR

Keep in mind that anytime the dealer gets access to your truck they likely install any updates for software throughout the truck. It probably has nothing to do with this, but it’s another variable that should be considered in troubleshooting.

Some service advisors are clue-free. Others seem to feel an obligation to deny knowledge of well known issues. Some are very good. I received a total runaround from my selling dealer regarding the TSB for the transmission cooler bypass valve set temperature change, but usually they are pretty good. I still can’t get an audio file to upload, and I am not going to set up a YouTube account for it. However, if your truck briefly sounds like a diesel for 1/4 to 1/2 second very shortly after it starts, that’s the oil pump priming issue. It occurs after extended shutdown because some oil drainback occurs creating an air gap in the pump intake path. It is normal, it occurs more in colder weather and with longer shutdown times.

Did you note the engine and transmission temperatures when this occurred? It could have been a high temperature protection mode. My other guess would be the 10 speed transmission valve body failure issues (hopefully not), but if temps were high while towing and it later returned to normal, it may have just been an overheat protection kicking in.

I took a 12 second video on my iphone but the file is too big to upload. I will have to figure out how to extract the audio or just do another start with an audio recording.

My plans changed today so I haven’t had a chance to record a start yet. This is one of the threads I recall, but you were involved so maybe you already reviewed this one:

Oil pump noise was discussed before. I will try to remember to record a remote start later this morning.

I don’t have detailed measurement data, but this past March we were hiking and camping in Death Valley and the Las Vegas area when this Spring’s heat wave hit with 105 plus temperatures and our 2021 L8T system kept our crew cab as cool as we wanted it (68F setting) with no trouble. Fan flows on auto once stabilized were fairly low. It seems like the OP’s system should be performing better.

Are you going to take long trips in it? If so, try out the seats in the various trims. For me the lower trim level seats were not comfortable.

I have had the same suspicion that some of these single use bolt installations are not actually torque to yield. In this case, the size involved and the initial torque, plus the additional rotation angle, don’t seem to be enough to be causing yield. However I have not done the actual calculations. One reason to use torque plus angle when not intending TTY is to reduce variation in the clamping force due to thread or head friction.

I have yet to see a set of GM wheels on a current generation HD truck (2020+) that I actually like. Least ugly is the best one can hope for in my opinion with the current GM wheels. The steel wheels actually look better than most of the alloys to me. Since they are the equivalent of work boots, I don’t let it bother me to the point where I consider spending money on wheels for the sake of looks. Luckily the 18” ones that came with my 2021 don’t scream ugly at me - they just whisper “can’t you at least notice how ugly I am once in a while.”

Is your truck not available for you to look? If not, can look at mine later this morning and post back. I suspect they are easily accessible.

Newdude posted while I was typing. If they didn’t have very good torque control with their impact driver or if they did the final quarter turn after applying 89 ft lbs, I agree with him they should be replaced.

Based on the service manual picture you posted, the four vertical bolts are single use and the torque specifications appear to be intended to be “torque to yield,” which permanently elongates the bolt. If they were torqued per that specification they should not be reused. However, if they used a properly limited impact device and only torqued them to the initial torque value of 89 ft lbs and did not do the final 70 to 80 degrees of additional rotation, they never yielded the bolts and they could be “reused” and torqued properly. The biggest issue in deciding whether to reuse them likely will be uncertainty over the torque applied by the impact driver.

Why the extreme lift?

The dealer I bought my truck from is actually pretty good. The problem is the labor force issues due to the dealer industry practices. They are struggling to keep experienced mechanics due to the pay structure, and the fluid change staff is minimum wage and uncertified. I still work with them when I need to, but I have had issues due to incompetence or lack of care as I described above. The unauthorized software update issue I suspect is driven by GM policy, but it is still an issue. It is my goddamn truck once i take delivery. You don’t modify it without my permission.

I view every visit to the dealer’s service department has a significant risk that they will do something wrong, use the wrong fluid, or change software without permission. Sometimes it’s unavoidable, and usually everything is fine (other than you never know what fluids they used), but I definitely try to minimize my exposure by doing everything I can on my own. I make them put on the work order that software is not to be updated without documented permission from me. Definitely inspect their work after fluid changes for loose plugs and filters, and incorrect levels. I have had all of these things happen over the years. I even had a dealer leave a connector disconnected after a minor fuel vent system filter recall on my Chevy Volt that bricked the car on the freeway when the lithium battery was depleted and the gas motor should have taken over. In another case, a friend coming over for dinner arrived at my house and I pointed out the trail (not drops) of oil behind his truck and noted oil still pouring out under the truck. He had just had his oil changed at the dealer and drove 20 miles to my house. We followed the trail back and found his oil drain plug a half block back along the road. If it had fallen out a mile sooner he would have gotten the red light and may have ruined his engine.

It is always a good idea to exercise it at least every few months to make sure the actuators don’t get stuck. It is also a good idea to actually drive it for at least a few hundred feet when you do that so seals experience motion and oil movement. Off pavement or snow/ice is best for this, but driving wet pavement in a straight line for a short distance will work if you don’t have other options. I have forgotten and gone as long as six months between exercising it on my 2021 and it has always shifted promptly. I usually just use my straight 300 foot gravel driveway.

The 6L90 in the 2020+ trucks has several improvements over the 6L90 in other trucks, so the comments made about issues with previous versions may not apply. I have been totally happy with the 6L90 in my 2021 3500 HD. The L8T has plenty of torque over a wide speed range and does not need to be held in a narrow rpm range unless you are towing near the maximum weight. Even then, six gears works just fine. Personally I don’t like what i consider the excessive shifting of most ten speeds, but i have not towed with one of these trucks with a ten speed. If you are buying used I would prioritize condition, miles, maintenance records, absence of stupid unreversible modifications, and towing history as more important than ten speed versus six speed. Make sure you try the seats out before choosing a trim level. I can drive my SLT with the leather bucket seat (premium pkg) option for 8 hours and get out feeling fine. I was uncomfortable in the SLE cloth seats with fold down center seat by the end of a 20 minute test drive. My wife loves the SLT leather bucket seats, too.

I have no first-hand knowledge about it but I have seen quite a few comments that GM selected lower viscosity gear oils to slightly improve fuel mileage. Personally, I care more about longevity and reliability than fuel mileage on this type of vehicle, and I have not read any cautions about using 75w90 in place of the 75w85 specified for the front differential, so I went with the 75w90 I have used for 35 years on other GM trucks and SUVs.

Because it has never used much oil, I haven’t monitored it closely enough to know for sure. However, the measured drop on my latest longer interval after our road trip of 4500 miles (nearly 0.6 quarts) was roughly proportional to the drop in previous 3750 miles intervals (a little less than 0.5 quarts), which would imply the drop is steady.

I received my truck with 2 miles on it and no other customer test drives, and I followed the break in carefully. I may just have been lucky though. My truck loses just under a pint in my 3750 mile oil changes intervals based on measuring added versus drained through 5 intervals now. I can’t ask for much better than that.

Also, I have noticed that prolonged high speed highway driving under some load (slide in camper wind resistance) seems to use a little more oil than general lower speed driving. This is for a 2021 with 19k miles that uses almost no oil between 3750 mile oil changes with Mobil One. It is based on my oil changes measurements after a 4000 mile Southwest parks trip this Spring.

Here are pictures of the specific Amsoil product I ordered (GL-5). The price was about $17.25 per quart plus a $10 six month membership fee. Shipping was free because the order exceeded $100 for six quarts. Valvoline in my local stores was around $18.

I changed the fluid in the rear axle of my 2021 gas 3500 hd last Fall at 15k miles. I used Amsoil Severe Gear 75w-90 in the squeeze packs. GM specifies slightly different oil viscosity ratings for the front and rear differentials for fuel mileage reasons, but 75w-90 is acceptable for both. Amsoil wasn’t any more expensive than other products on the store shelves. I did the short term membership deal and ordered 6 quarts to get free shipping. I don’t plan to change the front fluid until 30k. I removed the cover and wiped the inside of the cover and the differential housing as well as I could. It took 3.5 quarts to fill it to 0.4 inches below the bottom of the fill port. No additive is needed with the proper fluid type. I have 5000 miles since the change including some off pavement driving and the G80 locker behaves normally.