6.6 Chevy gas engine

on a somewhat related subject... I have often wondered why the 6.6gas is compared to the Ford F250 7.3 gas 10speed? wouldnt a more aligned comparison be with the Ford F250 6.2 6 speed? That is Ford's gas entry level in the F250 and is much closer in engine displacement than 7.3 vs 6.6 It would be apples to apples and yes, I realize you can get the 10 speed in the 6.2 gas version but it's only in the top trim level.

your points are well taken. I have heard rave reviews on the 10 speed Duramax. But... the 10 speed in the Duramax is not the one that would end up in the gasser. The gasser would be a different 10 speed. Another brand new trans. Ford / Gm worked on a joint venture to develop a ten speed trans. Ford obviously came out with theirs in the 7.3 Have no idea why GM didnt come out with their ten speed too. Time will tell.
Good to hear youre loving the powertrain. If I was going back to diesel that would have been my choice.

artie2908 wrote:
my 2020 came with 275/65-20R Goodyears. Just switched over to snow tires for the winter-- 275/70-18R The speedo is now off by 2-3 mph. at 60MPH displayed, I'm actually doing 57-58. One of the reported reasons for staying with the 6 speed was it's proven, whereas the 6.6 gasser was a brand new engine. Didnt want to press their luck with two major drivetrain components. also why put all the goodies in the first year? you need to make gradual improvements to stimulate sales. I am completely happy with the six speed. Would a ten speed be better?
Maybe. Maybe more complexity than is needed too. We have come a long way with Transmissions. My first car was a chevy 2 speed powerglide. Three speeds came next. Four speeds were state of the art. 6-8-10 speeds, at what point does it stop?
I test drove a Ford F250 7.3 10 speed, on two occasions. Nice truck but thought the trans was huntinng and bouncing around alot. Okay I was unloaded but still.
I guess it comes down to whatever makes you happy. Probably going to be at least 2022 or longer before GM comes out with their 10 speed in the gasser... if at all. If you find more speeds are that important buy a ford or the 8 speed 6.4 gasser from Ram. It's your money buy what makes you happy. What is great for me may not be great for you.

I am a GM truck buyer and I would not likely buy anything else, but I expect GM to put the best product forward that they can. I just don't think that happened with the 6.6 gas. I get the constant improvement mentality, but the 6.6 gas isn't so powerful that it can over come the other two HD trucks with more gears, especially with only 3.73's. It would be different if they didn't have a better tranny to pick from, but they do. I think the ten speed is a substantially better transmission. My 20 pulls better than my 18 does, noticeably better and the only difference is the transmission. If the difference is that noticeable with a diesel, I can only imagine how much better the gas engine would be. The ten speed doesn't hunt with the diesel, it is actually amazing how seamless it is. I am not sure if that would be the same with the gas, but I think that ten speed is very dialed in. I am glad your happy with your 6.6 gas and for you that's all that matters.

the trans(10 speed) behind the 6.6 duramax diesel is an Allison branded trans, whatever that means and the one behind the 6.6 gas is manufactured by GM. (6 speed)

Is the trans behind the 6.6 an Allison?

my 2020 came with 275/65-20R Goodyears. Just switched over to snow tires for the winter-- 275/70-18R The speedo is now off by 2-3 mph. at 60MPH displayed, I'm actually doing 57-58. One of the reported reasons for staying with the 6 speed was it's proven, whereas the 6.6 gasser was a brand new engine. Didnt want to press their luck with two major drivetrain components. also why put all the goodies in the first year? you need to make gradual improvements to stimulate sales. I am completely happy with the six speed. Would a ten speed be better?
Maybe. Maybe more complexity than is needed too. We have come a long way with Transmissions. My first car was a chevy 2 speed powerglide. Three speeds came next. Four speeds were state of the art. 6-8-10 speeds, at what point does it stop?
I test drove a Ford F250 7.3 10 speed, on two occasions. Nice truck but thought the trans was huntinng and bouncing around alot. Okay I was unloaded but still.
I guess it comes down to whatever makes you happy. Probably going to be at least 2022 or longer before GM comes out with their 10 speed in the gasser... if at all. If you find more speeds are that important buy a ford or the 8 speed 6.4 gasser from Ram. It's your money buy what makes you happy. What is great for me may not be great for you.

First question to 6.6 gas owners, do the 2020 gas HD's run 265 or 275 70/18's as OEM? Are you guys running OEM stock tire sizes? My 18 Duramax LB CC SRW 3500 gets 17-18 up to 70 mph. Over 80 it drops to about 15/16, running 275's now on that truck. I just pulled off the 285's which was an expensive test. Horrible mpg, lack of power, looked good, but not worth the offset in performance. My 20 DRW gets the same mileage as my SRW. I am running 245's instead of the OEM 235's on that DRW. I think this can be attributed to the 10 speed, the 20 is much heavier with a steel flatbed, 100 gallon offroad fuel tank and a steel storage box over the fuel tank and of course running an extra set of tires. Yet the MPG is nearly identical. I think if they would just drop the 10 speed in the 6.6 gas you would see at least 1-2 mpg gain empty and probably even better performance towing. I don't know what they are waiting for, using up 6 speeds sitting in a warehouse somewhere?

I have a 2020 GMC Sierra 2500 CC with the 6.6 gas. Got 6,000 miles on it, with about 2,000 towing a 7,000 lb RV trailer. Empty I get 15-16mpg if you baby it 17-18mph 10.5-11.4 towing I drive 65mph tops. I came from diesel pickups this is the first gas engine I'v had in 21 years. Love it. Not as powerful as diesel but it is no slouch. and none of the diesel emission headaches

You want the good or the bad news? Lol. Ok there both bad. Avrage about 14 without towing. Best qas 24. And 11 when towing. But i drive fast ( 80 plus on the highways here). Im guessing normal speeds would be about 17 or 18 without towing. My TT is loaded, so 5400 and the truck is loaded aslo, 3 people, bikes, electeic scooters, cooler, extra propane, tool box ( loaded up) inflatavle boats, so loaded for a weeks trip. Good news is it tows and rides nice, is fast( i can easily pass someone while towing) and stops on a dime. I didnt get it for mileage. TBH isnt much worse MPG then my jeep.

I'm very interested in this engine/drive train too.