C/K Man

Agree. Maybe in medium duty with a lower compression ratio. Port injection is easier to convert to gaseous fuel, though there CNG conversions of LT 5.3L's. I just wonder what the purpose of this LX 454 engine is.

Yes, the compression ratio is high, but why the 6.0L sized truck intake manifold and throttle body? The engine makes no sense unless it is built for some specific purpose. The high compression ratio would be appropriate for CNG/LNG, but the stated fuel is gasoline. And what does 'OEM Test Unit' mean?

No question the L8T 6.6L is a worthy successor to the L96 6.0L. It is very close in output to the Ford 7.3L and seems to deliver better fuel economy. Nonetheless for the last couple of years there has been persistent rumors that GM is considering an even larger gasoline V-8, possibly primarily for larger commercial trucks and other OEM's. For the last 6 months or so the rumors have died down a bit, but recently something showed up on GM Powertrain's website that has me wondering. What it is is a 454 cubic inch V-8 based on the LS family using the tall deck LSX high performance engine block. Now before you say that engine is old news and is just a high performance (and expensive) crate engine, the engine I am talking about is a different one. This one is a nearly completely dressed production engine that appears to use L96 intake, throttle body, and heads. In fact, the extra row of head bolts on the LSX block are visible but not used as they would be with LSX style heads. Defiantly a truck/commercial engine, and the website lists it as an 'OEM Test Unit' whatever that means. Could this be the rumored larger gasoline V-8?: https://gmpowertrain.com/products/lsx-454-engine/

Here we go again! The stuff is called NoxRust, GM has been using it since 1987, it's probably better than paint if you touch it up occasionally, and yes it can be messy. There have been rumors that GM is going to go to an E-coat paint process on their full size truck chassis, but it has not happened yet. Maybe 2022?

Remember GM came very close to offering a 4.5L Duramax about 10 years ago, but found that it wasn't any cheaper to manufacture than the 6.6L and didn't get any better fuel economy. It just made less power!

A gas option is supposedly coming for the Silverado 4500/5500/6500.

For many years, the Duramax's torque output was limited by the capacity of the 6 speed Allison transmission. Story I hear is the new 10 speed Allison is capable of much more, and we may see higher torque rating with the HD MCE in 2022 or 2023 (anyone know?).

Check engine light on? Check fuel pressure?

Ford's 'Death Wobble' can be very violent. The 'Chevy Shake' issue is a minor annoyance. They are 2 very different issues, I believe Ford's problem is due to the radius arm SFA front suspension design, as Jeeps use a similar design and have the same problem. I would not at all be surprised if Ford goes to IFS on the next Super Duty redesign.

At least GM follows J2807, I hear some other manufacturers don't.........

I have heard the 7.3L needs higher octane fuel. With that large bore it probably needs dual ignition like the 6.2L Ford. Are the spark plugs coming out of the heads like the old Ford Modulars? I wonder how the head gaskets will hold up on the 7.3L long term.

The L8T/6L90 combination is a fine base gasoline powertrain for the Silverado/Sierra HD's. I do think GM really needs to offer a gas engine option in the Silverado medium duty 4500/5500/6500 and 6500XD LCF as well, and the L8T might not be big enough for those applications. Before Covid there were a lot of rumors that a much larger 8L+ V-8 was in the works for the medium duty commercial trucks, and there was some speculation that such an engine might find its way into the Silverado/Sierra HD's. However, I have not heard anything about a larger V-8 since earlier this year, so maybe the project was dropped or it was just a rumor to begin with.

One thing I like about the l8t is it is now (2021 MY) available in a Flex Fuel E85 version. The Ford 7.3L is not.

Firing order is the same as any Big Block. Gear drive cam is different as is the distributor gear, but the distributor still turns clockwise.

Check the wiring. It you can get a scanner, check the data stream for the body control module and see what the ambient air temp. signal is or if there is an open or shorted circuit to the sensor.

Ford the record, the 10 sped automatics in the GM 1500's are similar to the 10 speeds in the F-150. Those were the jointly developed RWD 10 speed automatics. The 10 speed HD Torq-Shift for use in the Super Duty is a 'scale up' of the joint venture 10 speed, similar design but larger for increased capacity. The 10 speed Allison 10L1000 is not related to the joint venture transmissions or the 10 speed Torq-Shift. GM did that one themselves with help from Allison. Notice that the base model F-250 Super Duty still uses the 6.2L gas V-8 with the old 6 speed automatic from the F-150 (named Torq-Shift G). For that reason I think that GM may want to keep the 6L90 behind the L8T as the base HD powertrain to keep the price down for fleets. Offering the Allison 10 speed as an option with the L8T may make some non-commercial customers happy if it comes with better performance and economy. Also some have pointed out that the 7.3L is the optional gas engine in the Super Duty, while GM does not offer a larger gas engine as an option. There were rumors of a larger gas engine for commercial trucks, perhaps something is coming for the HD pickups as well. If so, I think it would be a sure thing that a larger gas engine would come with the Allison 10 speed.

Good question. For me the L8T 6.6L/6L90 drivetrain would be fine. I particularly like the fact that the 6L90 is a proven reliable transmission that shifts well and is not 'busy' like a lot of 10 speeds. Have not heard anything bad about the Allison 10 speed, but on 'Ford-Trucks.com' there are a lot of negative comments and experiences with the Ford HD 10 speed, particularly with the 7.3L gas.

Looks like Chevy will introduce a heaver version of the 6500XD LCF for 2021. The new 7500XD will feature a 33,000lbs. GVW.. Believe it of not, still with the Isuzu 5.2L 4 cylinder diesel.

2011 should be an L96. Yes, knock sensors are on the either side of the block, right between the starter and engine mount, left between the oil cooler lines and engine mount. They may have thermal insulators covering them. Much better location, they seldom give trouble since GM moved them.

Someone was saying the 2021 HD chassis was going to an E coat/paint process, but I never heard it mentioned anywhere else.

Any word or rumors about 2021 HD changes beyond what we have seen in the order guides? I am not expecting much, but I think 2022 may bring an MCE.

Having that issue on our new 6500's as well.

This is not a big deal. 'Monitors' are basically self tests the engine computer performs on certain components. In order to run all the tests, the truck has to be driven through various cycles of warm up, acceleration, deceleration, and steady cruise. Usually these self tests will all run in a day or two of normal driving.

I am not sure you would even need one on these modern DI engines, the crankcase ventilation system has oil separators built right into the valve covers. If someone did rig up a catch can on a new 6.6L L8T, it would be very interesting to see if any oil ended up in it.

Best of luck to you, it really isn't that hard to make the ABS work right. As for the previous owner, it never ceases to amaze me how much time and effort someone will put into fixing something the wrong way.