Lower Gears for Better Towing

Rabbittown · July 26, 2021

A few weeks ago, my wife and I decided to upgrade to a 12k fifth wheel. It’s well within the specs of my truck on pin weight and towing capacity. We just got back from our maiden voyage, and, overall, I’m pleased with the performance of my truck. However, on some of the steeper grades, it did have trouble maintaining speeds and was above 5000 RPM’s.

I love my truck and have no real desire to go back to a diesel and all their headaches. But, my wife and I have a couple of cross country trips planned to Acadia, Yellowstone, and the Tetons, and I’m concerned about some of the grades I might encounter. I’ve considered having a local shop that I trust upgrade me to 4:30 gears and putting in a cold air intake to increase torque.

Has anyone considered something similar? Am I being paranoid? Do you think the change in gear ratio would make a big difference?

Grumpy Bear · July 26, 2021

You could pull Mt. Evans with a steep enough gear and a 36 Ford flathead. But to run faster at lower rpm you don't need steeper gears. You need motor torque and earlier. Like diesel earlier. Lower gears at the same speed will either result in even more rpm assuming your already in high gear, or and up shift if your not. The question is less about speed and rpm and more about torque at the axle at whatever speed your trying to maintain. There is no free lunch.

CamGTP · July 26, 2021

You can't do it even if you wanted too.

There is no tuning options available as far as I know for the 6.6 gas engines. You could never program the truck to run correctly and shift correctly. And the cold air intake isn't going to help much at all. The factory airbox already pulls the coolest air in from the fenderwell.

Ray Pickle · July 26, 2021

Gas engines peak h.p. and torque occur at higher rpm than that of diesel, why I agree a lower gear ratio would help, high rpm operation will be necessary when max power is required. Diesel engines operate the same way but their peak torque and h.p. are achieved at far lower rpm. I have pulled a 12k fiver over all the terrain this country has to offer and wouldn't change a thing. My truck has 31k on the clock approximately 13k of it pulling fiver, if that maybe 40 miles of that pulling summits in the rockies. In those 40 miles a diesel would definitely be better otherwise I will stick with my gasser to live with for the 99% of the rest of my driving.

Another JR · July 26, 2021

About a 10k or 12k trailer is about the point where i think one should consider buying the diesel, but only if you tow much of the time. For me, towing an 8k boat, going slower up those rare few grades where i have to is not a big deal. The grades aren’t that long, and 50 really isn’t that slow anyway.

Rabbittown · July 27, 2021

12 hours ago, Ray Pickle said:

Gas engines peak h.p. and torque occur at higher rpm than that of diesel, why I agree a lower gear ratio would help, high rpm operation will be necessary when max power is required. Diesel engines operate the same way but their peak torque and h.p. are achieved at far lower rpm. I have pulled a 12k fiver over all the terrain this country has to offer and wouldn't change a thing. My truck has 31k on the clock approximately 13k of it pulling fiver, if that maybe 40 miles of that pulling summits in the rockies. In those 40 miles a diesel would definitely be better otherwise I will stick with my gasser to live with for the 99% of the rest of my driving.

It’s really helpful to hear your experiences with a similar setup. It sounds like I’m just being paranoid, which I’m prone to be in things such as this. The truck towed the camper great, and I was able to tow it up a 7% grade at 60. But, with it at 5000 RPM’s, I started getting nervous about how it might do when I get in the mountains around Acadia and the Tetons. 90% of the time, I was towing 2000-2500 RPM’s and cruising through rolling hills. Starting it on hills, I could definitely feel it back there, but I could get off the line okay.

Rabbittown · July 27, 2021

10 hours ago, Another JR said:

About a 10k or 12k trailer is about the point where i think one should consider buying the diesel, but only if you tow much of the time. For me, towing an 8k boat, going slower up those rare few grades where i have to is not a big deal. The grades aren’t that long, and 50 really isn’t that slow anyway.

That’s how I felt when I bought the truck. I only go one one major excursion every year where I might really challenge the truck. 95% of where I tow is in the Southeast, and there’s nothing here that I’m worried about. All combined, I probably take 6-8 trips per year, and the diesel just doesn’t seem worth it, especially after the experience I had with my f250 6.7.

Grumpy Bear · July 27, 2021

1 hour ago, Rabbittown said:

It’s really helpful to hear your experiences with a similar setup. It sounds like I’m just being paranoid, which I’m prone to be in things such as this. The truck towed the camper great, and I was able to tow it up a 7% grade at 60. But, with it at 5000 RPM’s, I started getting nervous about how it might do when I get in the mountains around Acadia and the Tetons. 90% of the time, I was towing 2000-2500 RPM’s and cruising through rolling hills. Starting it on hills, I could definitely feel it back there, but I could get off the line okay.

Being a fan of Brit Singles and Harley Davidson motorcycles my hair was standing on end when I bought my first Honda CB750 K6. I'd never ridden anything that would spin 4500 rpm all day every day year after year. Felt...well...unnatural. But I'd never ridden anything with a 2.5" stroke either. I still prefer rolling along at something under 2K.

No one is ever going to get the service life out of a 6.6 gasser spinning 4K all the time they would from a 6.6 LP5 Duramax lugging along at 1600 rpm. But for what you are doing

MORSNO · July 27, 2021

10 hours ago, Grumpy Bear said:

No one is ever going to get the service life out of a 6.6 gasser spinning 4K all the time they would from a 6.6 LP5 Duramax lugging along at 1600 rpm. But for what you are doing

The truck will be falling apart before the engine wears out, even with a gasser. Modern gas engines outlive their predecessors by hundreds of thousands of miles, it's not uncommon to see 500,000 6.0 gas engines and I suspect the new 6.6 will do the same. Heck we can get a new crate engine for less than injectors on a diesel which do wear out.

Grumpy Bear · July 27, 2021

12 minutes ago, MORSNO said:

The truck will be falling apart before the engine wears out, even with a gasser. Modern gas engines outlive their predecessors by hundreds of thousands of miles, it's not uncommon to see 500,000 6.0 gas engines and I suspect the new 6.6 will do the same. Heck we can get a new crate engine for less than injectors on a diesel which do wear out.

Good to know they are durable. But caution on the boasting. We've had some pre war gas motors go a million and several post war Ford FE motors close to a million. 300 gas six, a million is baked into the cake. Early 225 Dodge sixes I don't think will wear out if there is oil in them :crackup:

Yes yes, I get your point but those gassers your talking about didn't LIVE at 5K plus day in and day out either. (that was the OP's concern, right) Neither did the motors I just mentioned. See my point? You could run a Duramax at peak torque rpm till the middle east runs out of oil before you break it.

RyanCawdor · July 27, 2021

1 hour ago, Grumpy Bear said:

Good to know they are durable. But caution on the boasting. We've had some pre war gas motors go a million and several post war Ford FE motors close to a million. 300 gas six, a million is baked into the cake. Early 225 Dodge sixes I don't think will wear out if there is oil in them

Yes yes, I get your point but those gassers your talking about didn't LIVE at 5K plus day in and day out either. (that was the OP's concern, right) Neither did the motors I just mentioned. See my point? You could run a Duramax at peak torque rpm till the middle east runs out of oil before you break it.

I agree with you, the Duramax engine is excellent and will run and run forever. The problem is all of the emissions junk they put on them which is the weak link (unless the truck went on a diet). The def heater, egr, nox sensors, dpf etc... will likely have issues before the engine will. I can repair a lot of these items after warranty is up but I'm getting older and not sure if I want to. Another big concern is having one of these items fail while 1,000 miles from home and finding someone to work on it.

I'm still on the fence about whether to get a new gas or diesel truck. I loved my L5P.

Ray Pickle · July 28, 2021

It is an obvious conclusion that a gas engine will wear out premature if it " lives" at 5k rpm. I cannot fathom a scenario where that would be the case. I have pulled a number of passes in the rockies from monarch pass, from Dubois to Tetons, up and through Eisenhower tunnel, saw 5k for short duration on both Monarch and Eisenhower while keeping speed close to 50 mph. It was unnecessary but when you have a long days drive sometimes you do stuff like that! The wear effect that had on my engine was minimal and I have zero concerns about its long term durability as a result of how it is being used. Will it last as long as an unloaded truck that only cruises highways making deliveries and racking up huge annual miles, probably not. But I am expecting it will last a long time and be very economical to maintain. I base my opinions on the experience of 42 years in the automotive repair field, it may not make me any more knowledgeable than anyone else but there is a possibility. I would further agree with the obvious conclusion that a diesel has more torque than a like sized gas engine and that a corvette is faster than a chevette!

KARNUT · July 28, 2021

Generally my pulling gas engines would live around 3K pulling at highway speed pulling heavy. Diesels 1K less. It has to do with TQ. I last had a pulling rig in the early 2000s. Generally it would be in a non overdrive gear. So empty overdrive was available when not pulling. Prior to overdrive they would live at 3K pulling or not. Usually the early gas engines would get a refresh at 100K or traded in.

Rabbittown · July 28, 2021

7 hours ago, Ray Pickle said:

It is an obvious conclusion that a gas engine will wear out premature if it " lives" at 5k rpm. I cannot fathom a scenario where that would be the case. I have pulled a number of passes in the rockies from monarch pass, from Dubois to Tetons, up and through Eisenhower tunnel, saw 5k for short duration on both Monarch and Eisenhower while keeping speed close to 50 mph. It was unnecessary but when you have a long days drive sometimes you do stuff like that! The wear effect that had on my engine was minimal and I have zero concerns about its long term durability as a result of how it is being used. Will it last as long as an unloaded truck that only cruises highways making deliveries and racking up huge annual miles, probably not. But I am expecting it will last a long time and be very economical to maintain. I base my opinions on the experience of 42 years in the automotive repair field, it may not make me any more knowledgeable than anyone else but there is a possibility. I would further agree with the obvious conclusion that a diesel has more torque than a like sized gas engine and that a corvette is faster than a chevette!

So, just doing some quick math, I’m expecting to tow my fiver about 2000 miles next year. That amounts to about 16% of my total driving in the truck. Out of that, it would only be a small percentage of time that it would be pegged out at 5k. The rest of my driving is primarily unloaded and highway. I feel confident I won’t inflict any real damage to the engine with that small of a sample size. Even if I have to travel slower over steep passes, the gas truck still just makes the most sense for me. If the option for lower gears does open up, I may still jump on it to help starting on steep hills and accelerating on to the interstate, but I think I’m fine.

Thanks for helping me think through that!

Ray Pickle · July 29, 2021

16 hours ago, Rabbittown said:

So, just doing some quick math, I’m expecting to tow my fiver about 2000 miles next year. That amounts to about 16% of my total driving in the truck. Out of that, it would only be a small percentage of time that it would be pegged out at 5k. The rest of my driving is primarily unloaded and highway. I feel confident I won’t inflict any real damage to the engine with that small of a sample size. Even if I have to travel slower over steep passes, the gas truck still just makes the most sense for me. If the option for lower gears does open up, I may still jump on it to help starting on steep hills and accelerating on to the interstate, but I think I’m fine.

Thanks for helping me think through that! Your right on the money. 5k towing would be less than 1% of towing mileage and an imperceptible fraction of the overall miles you drive. If you are willing to downshift prior to ascending you will minimize the over revving that comes with allowing the computer/transmission to recognize you are ascending a steep long incline. By the time it figures it out the vehicle bleeds off so much momentum a 2 or 3 gear downshift is required thus redlining the engine. Slower speeds and manual downshifting can eliminate the 5k plus engine speeds darn near entirely. Remember the difference between ascending a long pull like Loveland pass at 50 mph and 40 mph is 2 or 3 minutes!