GM 6.6 gas

[LITEPHIL]

Not much talked about here on the new GM 6.6 engine. Whats the thoughts from people that own one? I may be interested in getting one next year if it has the 10 speed transmission.
Wish there was a bit more published testing other than those two guys that don't seem to really know what they're doing. Please don't refer to them since the test they did mentioned that the truck was floored and it showed the RPMs at like 3600 or what ever it was. But any real life input would be appreciated.

[noteven]

Is there something wrong with the Allison transmission in GM pickups?

Other than it doesn't have 4 overdrive speeds mostly useless for towing?

[colliehauler]

Groover wrote:

colliehauler wrote:
I remember when the old power glide automatic only had 2 speeds.

My family had a '63 and a '67 BelAir. The '63 had the 230 6 cylinder. It didn't have enough torque to use a third gear anyway so we really didn't notice the absence of a gear very much. The '67 had the 283 and always sounded like it needed to shift again but it was reliable and held up for quite a few miles. Then we got a '70 Impala with a 350 and a 3 speed transmission. Compared with the '67 it was bigger, more powerful, better to drive and gave better fuel economy. I inherited it in 1980 and drove it for 22 years. I only got rid of it then because I inherited a newer vehicle.

If you think that a 2 speed transmission was lacking my father used to talk about the '53 Buick with a single speed transmission but two torque converters.

Buick Dynaflow

If I remember correctly it was capable of being push started even though it had a automatic. Dad use to have a old early 50's Roadmaster with the big straight eight engine. In the Greyhound Museum in Hibbing Minnesota Greyhound use to use the big straight eight motor in a few of it's in town transit buses.

The irony of a 6 speed not being sufficient considering where we come from. Still don't understand why GM is not using the 10 speed when it was a joint venture between Ford and GM?

[Groover]

colliehauler wrote:
I remember when the old power glide automatic only had 2 speeds.

My family had a '63 and a '67 BelAir. The '63 had the 230 6 cylinder. It didn't have enough torque to use a third gear anyway so we really didn't notice the absence of a gear very much. The '67 had the 283 and always sounded like it needed to shift again but it was reliable and held up for quite a few miles. Then we got a '70 Impala with a 350 and a 3 speed transmission. Compared with the '67 it was bigger, more powerful, better to drive and gave better fuel economy. I inherited it in 1980 and drove it for 22 years. I only got rid of it then because I inherited a newer vehicle.

If you think that a 2 speed transmission was lacking my father used to talk about the '53 Buick with a single speed transmission but two torque converters.

Buick Dynaflow

[colliehauler]

I remember when the old power glide automatic only had 2 speeds.

[trailrider]

I have over 7000 miles on my 2020 Silverado 3500 6.6 GAS. It is definitely an improvement over my 2016 Silverado 3500 6.0 GAS. It gets a little better fuel mileage and I definitely notice the increased torque on the hills hauling all the camping stuff. Six speeds is plenty for me moving 19000 pounds of stuff. Three speeds used to work for me also in the past. Imagine that!

[Groover]

ksss wrote:
I would love to know what GM was thinking by not using the 10 speed in the 6.6 gas HD. Maybe supply issues? Whatever the reason it is costing them sales. The 6 may be ok, but the 10 speed would be better. The 10 speed provides 4 more opportunities for the truck to run in its power band, it would likely make the 6.6 feel more powerful. I would like to test drive one myself just to see what its about.

The 10 speed transmission certainly helped Ford get the power to the ground.

Ford 10 speed vs 6 speed drag race

[BurbMan]

The 10-speed was a joint dev effort between Ford and GM so not sure why Ford is in market with it sooner? The 8L90 8-speed has also been around so not sure why you can't get it in a truck?

[ksss]

I would love to know what GM was thinking by not using the 10 speed in the 6.6 gas HD. Maybe supply issues? Whatever the reason it is costing them sales. The 6 may be ok, but the 10 speed would be better. The 10 speed provides 4 more opportunities for the truck to run in its power band, it would likely make the 6.6 feel more powerful. I would like to test drive one myself just to see what its about.

[kellem]

Geo*Boy wrote:

gmckenzie wrote:

Geo*Boy wrote:
I would wait for the 8/10 speed and 4.10 gears, then GM will have a nice gas truck.

Partly why I'm thinking Ford. Downside is I think the 7.3 is dumbed down a bit too much.

I like what Ford did with the motor but I like the small block GM motor and I am not a fan of the empty ride of a Ford HD truck.

The 6.6 back in the day would have been considered big block, 402 ci.

I've had (2) 3/4 tons.....1 chevy and a Ram, both kicked like a mule empty.

[Geo_Boy]

gmckenzie wrote:

Geo*Boy wrote:
I would wait for the 8/10 speed and 4.10 gears, then GM will have a nice gas truck.

Partly why I'm thinking Ford. Downside is I think the 7.3 is dumbed down a bit too much.

I like what Ford did with the motor but I like the small block GM motor and I am not a fan of the empty ride of a Ford HD truck.

[Grit_dog]

lly-zf6 wrote:


My guess is it would be fine at 14k as long as you don't live in the Rockies.

He do.

[noteven]

Gas engine automatics head for whatever speed is direct once pulling power is needed. Multiple overdrives are great for empty truck, downhill, and downhill with tailwind.

4.30 rear ratio and normally aspirated gasohol engine would likely make a nice combination.

The Fast Lane Truck channel ran a 7.3 gas Ford loaner with 4.30 ratio up “The Ike Gauntlet” - he towed pretty good compared to other higher geared trucks.

[gmckenzie]

Geo*Boy wrote:
I would wait for the 8/10 speed and 4.10 gears, then GM will have a nice gas truck.

Partly why I'm thinking Ford. Downside is I think the 7.3 is dumbed down a bit too much.

[Lwiddis]

without the 10 speed transmission, I wouldn't consider it.

[Geo_Boy]

I would wait for the 8/10 speed and 4.10 gears, then GM will have a nice gas truck.