2023 6.6 Gas Real World Towing Observations

Jettech1 · March 17, 2023

4 minutes ago, the wanderer said:

Possibly. But Ford's 7.3 is quite a bit stronger yet than the 6.6, and all these 2500 gassers seem to be in the same rough hp/displacement so maybe it's less a carrot issue and more a simple engineering issue; it's just harder and harder to make more power with a N/A gas engine.

If getting a stronger gas engine means less reliability than I don't think that tradeoff is worth it. Gas should always be the cheap/reliable option.

I've always felt that the first brand which comes with a mid range diesel will take a lot of sales; something like 700 to 750 lb/ft of torque and focus on low end grunt with MPG savings and completely ignore high power outputs, save that for the HO diesels.

Then we'd have a good option between entry gas and completely bonkers diesel. I don't need to pull 35K pounds, but I'd love to pull 15K pounds at 15 to 20 mpg (pipe dream, I know, just sayin.)

I totally agree. The technology is there, why aren't they using it? Perhaps there's not enough people who would buy what you are talking about. I would for sure. I believe these hp and tq wars are insane. It's alway great to have plenty of each to do the job, but is it really necessary to have close to or over 1000 lb ft of torque? When is that much torque necessary? I pull our 8k lb camper with ease with just 464 lb ft of tq. Sure it would be nice to have more but isn't it always. I love your numbers for a diesel engine. If they produced one, I'm in for sure!!

nick112288 · March 19, 2023

On 3/17/2023 at 7:07 PM, the wanderer said:

Possibly. But Ford's 7.3 is quite a bit stronger yet than the 6.6, and all these 2500 gassers seem to be in the same rough hp/displacement so maybe it's less a carrot issue and more a simple engineering issue; it's just harder and harder to make more power with a N/A gas engine.

If getting a stronger gas engine means less reliability than I don't think that tradeoff is worth it. Gas should always be the cheap/reliable option.

I've always felt that the first brand which comes with a mid range diesel will take a lot of sales; something like 700 to 750 lb/ft of torque and focus on low end grunt with MPG savings and completely ignore high power outputs, save that for the HO diesels.

Then we'd have a good option between entry gas and completely bonkers diesel. I don't need to pull 35K pounds, but I'd love to pull 15K pounds at 15 to 20 mpg (pipe dream, I know, just sayin.)

On 3/15/2023 at 5:50 PM, Doodle said:

Actually the 6 speed is geared low enough from 1-3 it gets the load moving pretty good without a ton of revving. Where the flat spot is is from 3-4th. Think the 10 speed will help that. Sure it will rap out to 5K if I was flooring it all the time but if I just take my time it doesn’t scream too much. Braking is fine with the load but not having an exhaust brake like my LML has does suck. It will downshift some to help slow the load in tow/haul but it’s nothing like the exhaust brake on the diesel. I had a pretty good squat with it compared to my 2015 with air bags, but I will tell you it handles the load better than the 2015 with air bags in my opinion. Frame is pretty stout on the 2020+. It sits up a lot higher than my 2015. I was only 65 yesterday but trans temp never went above 165. I’ve never seen it get higher than that but I haven’t pulled in 100 degree heat yet either.

I will say this thing tows way better than the old 6.0 4-speed I had but that was a 2005 so really can’t compare that at all to the newer 6.0L with the 6 speed. I’ve never actually driven one of those.

I kept hoping maybe GM would up the HP/TQ on the L8T with the refresh but so far they haven’t and probably never will. I think something like 450HP/500TQ in a gas would just about meet most everyone’s needs for towing with a gas. That would help in the elevation areas. I know some will think providing a better gas engine will hurt diesel sales, quite honestly wouldn’t GM be better off anyway then you don’t have all the crazy expensive emissions warranty claims? Just my $0.02.

A GM big block rumor kept popping up right before COVID really kicked in. Something to compete with the 7.3L from Ford. Possibly a modern 454.

But as I said that was before COVID. Since then nothing has been mentioned anywhere.

I bet a modern 454 could easily get the 450/500 mark. Especially since the 7.3 is at 430/480 and it isn't even direct injection.

Jettech1 · March 19, 2023

1 minute ago, nick112288 said:

A GM big block rumor kept popping up right before COVID really kicked in. Something to compete with the 7.3L from Ford. Possibly a modern 454.

But as I said that was before COVID. Since then nothing has been mentioned anywhere.

I bet a modern 454 could easily get the 450/500 mark. Especially since the 7.3 is at 430/480 and it isn't even direct injection.

I bet the current 6.6 gasser could get to those numbers easily. There are so many factors that we don't know about when it comes to...well...everything concerning the decisions car makers make.

nick112288 · March 19, 2023

1 hour ago, Jettech1 said:

I bet the current 6.6 gasser could get to those numbers easily. There are so many factors that we don't know about when it comes to...well...everything concerning the decisions car makers make.

I'm sure you're correct, but obviously a bigger displacement would make it easier and generally less stressful on the engine itself.

Jettech1 · March 19, 2023

6 minutes ago, nick112288 said:

I'm sure you're correct, but obviously a bigger displacement would make it easier and generally less stressful on the engine itself.

A very valid point. But...when you look into how the 6.6 is built...It's way under powered. And marketing probably had a big role on its output. That engine is so well built, 401hp isn't even scratching the surface of what it's capable of.

Ray Pickle · March 20, 2023

On 3/18/2023 at 10:39 PM, nick112288 said:

A GM big block rumor kept popping up right before COVID really kicked in. Something to compete with the 7.3L from Ford. Possibly a modern 454.

But as I said that was before COVID. Since then nothing has been mentioned anywhere.

I bet a modern 454 could easily get the 450/500 mark. Especially since the 7.3 is at 430/480 and it isn't even direct injection.

On 3/19/2023 at 12:06 AM, Jettech1 said:

A very valid point. But...when you look into how the 6.6 is built...It's way under powered. And marketing probably had a big role on its output. That engine is so well built, 401hp isn't even scratching the surface of what it's capable of.

Way underpowered may be a bit of a stretch. 400 c.i.d. and 401 hp/464torque, vs 7.3 - 445c.i.d.@ 430hp/475torque. Based on numbers looks like 7.3 is a little weak for displacement. Not to be biased lets include the old and vaunted, GM 8.1- 496cid @ 345hp and 450 torque. Could they tune for more power especially with more octane, I am certain. But for maximimum reliabilty and commercial applications it was primarily intended for I think the numbers are pretty solid on regular gas. The 10 speed will bring its towing performance equal to 7.3 and it gets better fuel efficiency with the old 6 speed so I expect that will also marginally improve further beyond the Ford.

Jettech1 · March 20, 2023

35 minutes ago, Ray Pickle said:

Way underpowered may be a bit of a stretch. 400 c.i.d. and 401 hp/464torque, vs 7.3 - 445c.i.d.@ 430hp/475torque. Based on numbers looks like 7.3 is a little weak for displacement. Not to be biased lets include the old and vaunted, GM 8.1- 496cid @ 345hp and 450 torque. Could they tune for more power especially with more octane, I am certain. But for maximimum reliabilty and commercial applications it was primarily intended for I think the numbers are pretty solid on regular gas. The 10 speed will bring its towing performance equal to 7.3 and it gets better fuel efficiency with the old 6 speed so I expect that will also marginally improve further beyond the Ford.

There's also another part of this equation. When TFL put the gasser on the dyno, they got 328hp to the rear wheels. That's only a 18% driveline loss. Not many years ago that percentage of driveline loss to the rear wheels was ONLY with a manual transmission. So I think about the power coming off the crank to the 6L90, that huge driveshaft, that 11.5" differential, huge axles, giant brake rotors then onto 20" wheels and tires to the ground. I really don't see it being at a 18% loss. Maybe it's possible, but I have my doubts. Bottom line is I think it's under rated. Where I was coming from saying it's underpowered is that it has an iron block, forged crank, forged rods.....the possibilities here are insane. But for overall reliability with low octane fuel.....I can see that. I also can see GM bumping up the numbers with basically no changes to the engine.

Jettech1 · March 20, 2023

Here's a quick story of manufacturers lying about the actual numbers. I bought a new 2004 Titan when they first came out. I actually had #356 from the factory. It was an amazing truck and fast as hell. Nissan rated that 5.6L engine at 305hp. I took it to the dyno, it was putting down 270hp to the rear wheels of which equates to around a 12% driveline loss. That's not possible because that thing would eat up the 345hp hemi's and every other truck out there with ease. It became quite obvious Nissan was lying and they lied big time. My point is the numbers that are advertised don't always equate to real world numbers.

At the time I also had a 2003 Lincoln Aviator that was rated at 300hp. I put that on the dyno and it was spot on showing 230 at the rear wheels which is right at the expected 24% driveline loss. So who really knows what the actual hp numbers are until you put them on a dyno. And then it's still a little murky.

Ray Pickle · March 21, 2023

17 hours ago, Jettech1 said:

Here's a quick story of manufacturers lying about the actual numbers. I bought a new 2004 Titan when they first came out. I actually had #356 from the factory. It was an amazing truck and fast as hell. Nissan rated that 5.6L engine at 305hp. I took it to the dyno, it was putting down 270hp to the rear wheels of which equates to around a 12% driveline loss. That's not possible because that thing would eat up the 345hp hemi's and every other truck out there with ease. It became quite obvious Nissan was lying and they lied big time. My point is the numbers that are advertised don't always equate to real world numbers.

At the time I also had a 2003 Lincoln Aviator that was rated at 300hp. I put that on the dyno and it was spot on showing 230 at the rear wheels which is right at the expected 24% driveline loss. So who really knows what the actual hp numbers are until you put them on a dyno. And then it's still a little murky.

And then there are the dyno differences etc. Sometimes agenda driven by operator?

cbaker879 · June 10, 2024

Hello all,

I'm new here and new to the L8T 2500hd crew. We just took our first trip with our 10k 5th wheel trailer. With my previous gasser I could pull the trailer in 5th (6spd trans) gear with coolant temps not rising past 200 mark.

With the L8T it runs at 210 unloaded and loaded running in 4th. But when I let it shift into 5th also a (6spd trans) the temp immediately jumps up to about 230 or so. Is this normal? Or should I be having my dealership take a look at it

Truston Gunter · July 26, 2024

On 6/10/2024 at 10:34 AM, cbaker879 said:

Hello all,

I'm new here and new to the L8T 2500hd crew. We just took our first trip with our 10k 5th wheel trailer. With my previous gasser I could pull the trailer in 5th (6spd trans) gear with coolant temps not rising past 200 mark.

With the L8T it runs at 210 unloaded and loaded running in 4th. But when I let it shift into 5th also a (6spd trans) the temp immediately jumps up to about 230 or so. Is this normal? Or should I be having my dealership take a look at it

I think that's completely normal, I too am a novice so take my opinion very lightly. I'm curious what your trans temp and MPG's are. I have a lighter bumper pull trailer that has a big frontal footprint and get wildly less MPG's than anyone has posted here. Maybe I am an aggressive driver but I truly don't think so. The truck feels solid and here in south Texas, interstate speed limit is 75 MPH so I generally set the cruise at 77 and just drive. Even at that speed I'm usually getting passed but at no time do I feel unsafe. To maintain that speed I'm usually in 4th gear and its screaming at 3K rpms (although not really loud in the cab). The truck consumes oil when towing at high rpms, I've read this is not a problem for a gasser since its keeps it in the "power band". Coolant temp stays at 220, trans is at 205, MPG is at 5-6. Currently at 53K miles and no real issues thus far.

cbaker879 · July 30, 2024

On 7/26/2024 at 8:13 AM, Truston Gunter said:

I think that's completely normal, I too am a novice so take my opinion very lightly. I'm curious what your trans temp and MPG's are. I have a lighter bumper pull trailer that has a big frontal footprint and get wildly less MPG's than anyone has posted here. Maybe I am an aggressive driver but I truly don't think so. The truck feels solid and here in south Texas, interstate speed limit is 75 MPH so I generally set the cruise at 77 and just drive. Even at that speed I'm usually getting passed but at no time do I feel unsafe. To maintain that speed I'm usually in 4th gear and its screaming at 3K rpms (although not really loud in the cab). The truck consumes oil when towing at high rpms, I've read this is not a problem for a gasser since its keeps it in the "power band". Coolant temp stays at 220, trans is at 205, MPG is at 5-6. Currently at 53K miles and no real issues thus far.

I don't think my trans got over 200. But I'm not rolling at 75, at most 65-70