C/K Man

https://gmauthority.com/blog/2026/05/is-this-gmc-sierra-hd-prototype-testing-a-new-gm-gas-engine-for-heavy-duty-trucks/

Is Oshawa building LD's too? It will be interesting to see what will happen in Fort Wayne, that's where most U.S. LD's are made I believe.

Work is the Silverado Medium Duty trucks are being dropped. Dearlers are still taking orders but production ends on September 30th.. The reason seems to that International has sold the Springfield plant where these trucks are manufactured. The Isuzu based LCF models will continue. Rumor is GM may introduce new medium duty models with the 2029 Silverado HD's. The trucks will likely be produced by GM without a partner.

That is a flap that goes on either end of the cowl vent at the base of the windshield. Normally you can't see it because it is behind the fender. It is supposed to let water out of the cowl but keep hot air from the engine compartment from being drawn into the HVAC. It has a little weight on it to keep it closed.

I would like to see them bring back the E-85 option.

Monroe Equipment was the company that converted the Topkick and Kodiak.

You need a scanner that can read the ABS/stability/trailer brake systems. These are 'C' codes. If there isn't a trailer hooked up the problem could be with the plug if it isn't with your 3rd. brake light.

Sorry, should have said for 2027. I have heard rumors the Gen. 6 for the 1500's and SUV's will be in the form of a 5.7L and a 6.6L.

Any more news on the upcoming L8S? Will it be used in the 2028 HD's or is it the new 6.6L rumored for the 1500's in 2027?

'TFL' ran a piece featuring some footage of test trucks spotted in Colorado recently, and speculated that these trucks may have been powered by the 8.3L Duramax: https://tfltruck.com/2025/07/spied-are-these-the-new-2027-chevy-silverado-hd-gmc-sierra-hd-duramax-trucks-could-they-have-the-8-3l-megamax-v8/ A few days later, 'GMAuthority' posted word from a reliable source that the trucks were in fact powered by updated 6.6L Duramax diesels, and the rumored 8.3L is NOT planned for the HD pickups: https://gmauthority.com/blog/2025/07/is-the-8-3l-duramax-megamax-hiding-in-new-silverado-hd-sierra-hd-prototypes/ FWIW, I think the 8.3L Duramax does exist and is in the pipeline, but I think it's for larger commercial trucks.

I wonder if Fort Wayne will continue to build Silverado/Sierra LD's or will change to something else: https://www.wxyz.com/news/gm-moving-production-of-escalade-silverado-sierra-to-orion-assembly-plant-in-2027?fbclid=IwY2xjawLj0C1leHRuA2FlbQIxMQBicmlkETFXa3ZVc2tkakV1akxmZTdaAR4DvhDAc_l-S2xL7EtjddTFPja7i_md_WhZld8YamgVpixZNoFnKIjHf9RWEA_aem_c2TaGgBU7d_ZJJ-Sr-trEg

CAFE has to do with fuel economy, not emission controls. Emissions is EPA and CARB.

So, if the Corporate Average Fuel Economy requirements are essentially eliminated, what does in mean for the next generation Silverado/Sierra?

Sorry for not being the best picture, but this is a bore scope view of the #1 cylinder in my 145,000 mile 5.3L 2011 Yukon. This vehicle has been running on E85 about 80% of the time, never been apart.

Try a Fleetpride store.

E85 helps a lot too! I wish GM would make E85 capability at option on the L8T again.

A lot of people think that intake valve deposits are the only result of crankcase blow-by. That isn't true, a lot of the deposits are caused by the EGR affect of variable valve timing. Instead of using EGR valves like older engines did, modern VVT engines accomplish the same thing by advancing cam timing to the point that the intake valve starts to open before the piston reaches TDC on the exhaust stroke. This blows exhaust up through the intake port past the open intake valve, and the exhaust is almost immediatly drawn back into the cyinder on the intake stroke when the exhaust valve closes and the piston goes back down. The hot exhaust will condense on the cooler back side of the intake valve and port and that's what causes the deposits. Using a higher quality 'Top Tier' gasoline will reduce both intake valve and combustion chamber deposits. It's less of an issue in California due to the cleaner (and more expensive) gasoline formulation.

A friend of mine bought a new 2002 3500HD cab and chassis. This was a GMT400 series truck with the I-beam front axle and 5/10 stud wheels, and it had an 8.1L with the 4L80E transmission. Great truck, he still has it! Interesting that the last GMT400 cab trucks were actually 2008's. In Mexico, the GMT530 Kodiak stayed in production until 2008.

Yes, GMC's had a different dash and instrument cluster during that generation. Nice truck!

Sorry for the late answer. Canadian built GMC's during those years used Chevy engines.

Is that White Sands solid the same color that's on the 2026 Trailblazer? It's a nice color.

Looks like GM is staying with the wax frame coating, you can see where the assembly line frame cradle left smudge marks on the bottom of the side rails. The chassis doesn't look much different than the current model. Good catch on the sliding rear window.

Both the Chevy and International versions of the joint venture trucks use the current Duramax.

I would be willing to wager if a 6.6L is made available in the 1500's it would be an aluminum block engine similar to the current 6.2L, not an iron block derivitive of the L8T. I wonder if the 8.3L Duramax would have some commercial applications beyond GM trucks.

Article says the basic platform (chassis) will be unchanged. I guess that means for better or worse another generation of waxy goo covered frames. It appears so in the pictures. If they get the fender lips tighter around the wheels with that shape as in the photos, the trucks will look a lot better. I'll bet that truck is a GMC judging by the grille texture.