Disappointed in towing performance

GearHead71 · September 15, 2020

We drove up and back from Breckenridge this weekend. Same story. Any long uphill grades the truck could BARELY maintain the speed limit and in a couple instances couldn't maintain speed. I tried the following with no improvements:

Turning on cruise control

Turning off tow/haul mode

Putting it into "L" and manually downshifting

What's really weird about the last one is even when I tried to force it to downshift it wouldn't..... What's even stranger is it would be at 3500RPM at 55 MPH and when I'd try and manually downshift the RPMs would increase to about 3700 RPM but it wouldn't change gears.... I don't understand how that happens. I am going to call the dealer today and see what they can do, it feels like it's almost in a limp mode or something. I was getting passed by half tons pulling bigger campers than mine.

MTU Alum · September 16, 2020

The engine is restricting shifts manually or automatically to keep temps in check. I don't disagree that it is disappointing. It generally only happens on long grades at altitude. The truck won't break but you won't win any races either.

#iworkforGM

greatmizzou · September 16, 2020

I know my first tow, you must select the low gear and then it will let you manual adjust however you wish. I wasnt able to select gears in Drive

Bikemobile · October 12, 2020

I have been shopping that 6.6 alot and reading about it. TFL Truck said it didnt do well pulling max weight on the IKE.

Its a small block with 402 cubic inches. That should be enough but as said, with the 6 speed its not enough. I tow my 6000 pound (loaded) camper trailer with a 2017 5.3 and 8 speed. I live at 7700 foot elevation in the mountains of Colorado. I can go over monarch pass at 45-55 the whole way if I want to. You have to rev the snot out of the 5.3 to do it and engine goes up in temp but it gets the job done.

So It sounds like the gas 6.6 isnt really a great upgrade from the other small blocks. Wheres the big block?

greatmizzou · October 12, 2020

OP what octane fuel did you use? I have similar camper weight and had an opposite towing experience. Something doesn't seem right that it struggles that much with 6,000lbs

TrailBoss1 · October 13, 2020

I mentioned this before in another post. Remember the big block 8.1 Vortec? That was rated at 340 HP and 455 TQ. The curves were slightly different with the 8.1 being flatter but, on paper, the 6.6 produces both more peak horsepower and torque. And I believe the 8.1 was mated to a 4 speed transmission.

I agree the 6.6 Gas shouldn’t struggle with a 6000 pound trailer if it’s kept in the power band; at least when looking at the numbers on paper. I think the 4.10 axle would really help here in keeping the motor revs in the power band.

davester · October 13, 2020

The 8.1, at least with the GMT800 trucks, got the Allison, which is a 5 speed (later ones could be a 6 speed I think).

KARNUT · October 13, 2020

If there’s a problem pulling that weigh at 3500 RPMs at 55 mph. It’s not the transmissions fault.

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dieselfan1 · October 13, 2020

This is disappointing. I was thinking about a 6.6 gasser to tow my travel trailer. My 5.3 get the job done but it's a half ton . I need a truck with more ass to handle the long grades out west.

I watched the TFL video of the 6.6 gasser on the Ike gauntlet.

Mr. Truck had the same exact problem as the OP.

This motor needs the ten speed . I'm not even going to consider it until they make it available. 2021's still have the six speed. Sad.

I can't figure out why GM don't get with the program on these trucks. I'm not interested in a diesel either. Too much hassle and money. Meanwhile Ford and Dodge have the tools for towing .

rjpoog1989 · October 13, 2020

I have to say, this is very disappointing. It almost seems like they want to force me into a Diesel. Ram 6.4 didn’t fair much better in the IKE and it has an 8 speed. Ford Godzilla is really the only option for gas.

dieselfan1 · October 13, 2020

39 minutes ago, rjpoog1989 said:

I have to say, this is very disappointing. It almost seems like they want to force me into a Diesel. Ram 6.4 didn’t fair much better in the IKE and it has an 8 speed. Ford Godzilla is really the only option for gas.

For me, Ford is not an option. No thanks.

Gagliano7 · October 13, 2020

The Ford Godzilla beat the Chevy 6.6 by 3 minutes up the Gauntlet. The Ford has the 10 speed and it sounded like he said 4:30 gear which ford has an option. I think if the chevy had same trans and gears It would have been a very even race. Funny ford offers a 4:30 gear with the 10 speed and GM's only option withe the 6 speed besides the 3:73 is the 3:42. Laughable!!!

GearHead71 · October 13, 2020

23 hours ago, greatmizzou said:

OP what octane fuel did you use? I have similar camper weight and had an opposite towing experience. Something doesn't seem right that it struggles that much with 6,000lbs

I usually use mid grade which around here is typically 87

14 hours ago, TrailBoss1 said:

I mentioned this before in another post. Remember the big block 8.1 Vortec? That was rated at 340 HP and 455 TQ. The curves were slightly different with the 8.1 being flatter but, on paper, the 6.6 produces both more peak horsepower and torque. And I believe the 8.1 was mated to a 4 speed transmission.

I agree the 6.6 Gas shouldn’t struggle with a 6000 pound trailer if it’s kept in the power band; at least when looking at the numbers on paper. I think the 4.10 axle would really help here in keeping the motor revs in the power band.

I need to look up the torque and horsepower curves. I'm thinking about regearing, need to figure out if that will help my problem

4 hours ago, KARNUT said:

If there’s a problem pulling that weigh at 3500 RPMs at 55 mph. It’s not the transmissions fault.

Sent from my iPhone using Tapatalk

I haven't looked up where the truck makes its max torque and horsepower. If it's around 3500 RPM you are correct. But to me it feels more like around 4200-4500 RPM. That's why I feel like it's a transmission/gearing issue. There's no gear to keep me around 4500 RPM at 60mph.

11 minutes ago, Gagliano7 said:

The Ford Godzilla beat the Chevy 6.6 by 3 minutes up the Gauntlet. The Ford has the 10 speed and it sounded like he said 4:30 gear which ford has an option. I think if the chevy had same trans and gears It would have been a very even race. Funny ford offers a 4:30 gear with the 10 speed and GM's only option withe the 6 speed besides the 3:73 is the 3:42. Laughable!!!

I was surprised there was no gearing option lower than 3.73 for the gas. I'm considering going to 4.10 or 4.30 but need to do some more research. And figure out if anyone is regearing these trucks.

Ray Pickle · October 13, 2020

I think the "struggle" is in assuming or insisting truck programming is correct in every towing circumstance. Assuming an experienced driver you will find the 6 speed has a gear to get the job done. Manual mode is unfortunately there for a reason and all gas engine trucks will benefit from the driver reading the road and making proper decisions to keep engine in powerband. Do not "try" cruise control to alleviate your situation, the speed will scrub at least 3 or 4 mph before it attempts a downshift so you will already be behind the 8 ball. I have had zero problems manually downshifting preemptively on extreme ascents. This has been a rare occurrence towing a 12k fiver over 10k mi. with a 2020 gasser.

GearHead71 · October 13, 2020

1 minute ago, Ray Pickle said:

I think the "struggle" is in assuming or insisting truck programming is correct in every towing circumstance. Assuming an experienced driver you will find the 6 speed has a gear to get the job done. Manual mode is unfortunately there for a reason and all gas engine trucks will benefit from the driver reading the road and making proper decisions to keep engine in powerband. Do not "try" cruise control to alleviate your situation, the speed will scrub at least 3 or 4 mph before it attempts a downshift so you will already be behind the 8 ball. I have had zero problems manually downshifting preemptively on extreme ascents. This has been a rare occurrence towing a 12k fiver over 10k mi. with a 2020 gasser.

I guess a better way to say it is while towing if I lock it into 2nd gear before the hill my speed will be limited to about 59mph and that will be around 5500rpm. The only way to get to 60mph is for it to shift to 3rd gear which drops the rpms to about 3500rpm and I loose all power. I haven't been able to maintain 60mpm up a steep (long distant) incline.

Is there something else I should try?