Jay P

The newer LM2/LZ0s specify 200k for the oil pump belt and since nothing related has changed that would apply to the earlier models also. If it was mine I would replace it if the engine is apart for the timing chains.

The engine is mechanically the same as the Corvette 6.2l and that does use a higher viscosity oil so It should be fine.

DEF at the pump at a truck stop is usually the freshest (usually cheaper also). Heat and sunlight degrade DEF so don't buy the store stuff if it's sitting in the sun. Brand doesn't make much difference. Learn how to read the date code so you are getting fresh DEF. As for fuel additives, I don't use them unless there is a good reason (like antigel in the winter). Best is to just get good diesel from a station that has high turnover. Some swear by additives and some think they are snake oil, mostly a personal preference.

How old is the truck or how old are the sensors. They have batteries and don't last forever. The sensors read absolute pressure so elevation will affect the readings (unless you have a high end vehicle). They were never intended to be as good as a good tire pressure gauge, they are there to let you know you have an issue/flat tire.

The 6.6l is and always has been built in Ohio. Isuzu helped GM design it but they have been out of the picture for a long time and sold their part of DMAX Ltd a couple of years ago (after the initial design they helped with, it was mostly an investment for Isuzu). The 3.0l diesel was mostly designed in Turin Italy (with Opels help) and has always been built in Flint, MI. It was a new engine from the ground up. The 2.8l 4 cylinder diesel used in the Colorado/Canyon was an existing VM Motori engine and that company is now owned by Stellantis. It was owned by Fiat at the time when GM started using it.

Not missing anything. It's only a 3.0l engine so it doesn't do much especially if you compare it to the 6.6l diesel exhaust brake. Jay

2 Things: 1: the tpms sensors read absolute pressure (they don't have a way of comparing to actual outside air pressure) so they can be off from the reading on a good tire pressure gauge. Elevation can really mess with the readings. Some high end cars do adjust for atmospheric pressure in the BCM but Chev/GMCs don't. 2: The computer won't adjust pressure you see until you drive the vehicle. Most TPMS sensors need to get to about 40 mph to see the change. This is done so when the car/truck is parked the sensors go to sleep and don't kill the internal battery.

Local Autozone carries the correct Mobil 1. It's around $11 a quart.

AutoZone stores near me carry the Mobil 1 Dexos D oil. The factory oil is made by Mobil. I haven't changed the oil on the Tahoe yet but did several times on my 21 Silverado. The fuel filter is easy to change. FWIW the fuel filter assembly is the same one used on the 6.6l L5P trucks so the filter is easy to find. Don't buy fuel filters on Amazon, even when they say it's a GM/AC Delco filter it more likely a cheap knock-off. https://www.gmdexos.com/brands/dexosd/index.html

Don't have a 24, but a 23 Tahoe with the 3.0l. The LZ0 won't be in the SUVs until the 25 model year. This is my 2nd 3.0l diesel (1st was a 21 Silverado) and no worries about the belt. The recommended change for the belt is now 200K. As for fuel mileage the Tahoe gets between 20 and 28 MPG depending on highway vs city and how you drive it.

Unless you have the truck corrected for the 35" tires that is part of your problem. The transmission shift points were all set up using a stock size tire and a stock height truck. The tire will also mess up the ABS/Traction control/Stabilitrak. If you take it to the dealer they likely won't touch it due to the lift and bigger tires and will probably void your factory drivetrain warranty (unless the dealer sold it with the lift/tires). FWIW the 10 speed in my past 19 Sierra 6.2l, 21 Silverado 3.0l and current Tahoe 3.0l all shift fine. I do understand the feeling of the trans shifting since I put shift kits in most of my pre electronic transmissions. Jay

Send an email here. Make sure ask for a complete build sheet and to tell them it’s your truck (they charge for non-owners). They can send you a complete build sheet on your truck. Be careful asking a dealer for the build sheet as they have access to both the full build sheet and a shorter one that’s just window sticker info in a different format. [email protected] Here is the GM web site that leads to that email address. http://www.gmmediaarchive.com/?page=1

The original 8 speed (when it first came out) came with a different fluid than is installed in later models (2019 or 2020 may have been the last of the old fluid). The original fluid used absorbed water and that caused the shudder. The newer fluid doesn’t absorb water and helped. They have also had issues with the torque converters on the 8 speed. I don’t remember what year GM changed fluids but it’s possible it had the old fluid. I attached the TSB for the fluid change. TSB 18-NA-355,.pdf

Look at this TSB. 21-NA-141.pdf

I would give up heated seats for a heated steering wheel.... FYI I lived in MN until my job sent me to Colorado in late 2014 and I got out of that messed up state when I retired in 2022 (traffic between Colorado Springs and Fort Collins is worse that the Twin Cities metro area).

The local AutoZone stores in my area actually carry Mobil 1 ESP X2 which is a DexosD oil.

While I don’t know what the opening temp is for the TBV, there is nothing wrong with 175F for a trans temp. If your truck maintains temp empty but gets above 200F towing or loaded or hot outside air temp the thermostat may not be opening all the way (some fluid still bypassing the cooler).

https://www.gmc.com/bypass/pcf/gma-content-api/resources/sites/GMA/content/staging/MANUALS/6000/MA6525/en_US/6.0/23_GMC_Sierra_Sierra_Denali_1500_OM_en_US_U_84883874B_2022DEC14_2P (1).pdf

Your LB7 doesn't have any emissions and no post injection. Even the newest 6.6l has post injection (injection on exhaust stroke) to help light off the DPF regen cycle. The addition of a 9th injector in the exhaust reduced the post injection but didn't get rid of it completely. I have had all but one generation of the 6.6l Duramax and starting with the LMM the oil was black right after changing the oil. Jay

As of 2023 the oil pump belt is 15 years/200k miles. If the belt part hasn't changed then no reason an earlier model can't go 200k. Attached is a pic from our 23 Tahoe diesel supplement.

I had an issue with the Pulsar on my 19 GMC. If you look at instant fuel economy with it attached you will notice it never gets to 99mpg like it does without the Pulsar when coasting. I think it's not allowing the injectors to cut fuel when coasting and that why mileage drops. When I had the Range DFM disabler installed the milage didn't drop at all. Jay

If you put the transmission in M9 DFM will not be active. The range DFM disabler is hit/miss (10 speed only). It works for some and doesn't work for others. Don't know of any other options other than the Pulsar you mentioned. Jay

While I agree that $400 is too much, the windows comparison is not valid since there isn't a tech applying the update. If you take your computer to a repair shop and they have to apply an update you will be charged for the techs time. I would ask for a good will update since you are only 2 weeks out of warranty. Jay

I leave the charger on the tonneau cover where it's hard to miss. Jay

True but that connection is there to charge/maintain an RV battery (it can also provide power for electric brakes) so it has to be direct and the wire sized properly to do that.