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Old 07-31-2021, 08:36 AM   #1
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Torque, how much do I need

I now have a motorhome that weights approximately 40,000# and I tow an Expedition that weights approximately 5,700#. Our motorhome has 1,250 Ft Lb of torque and pulls the Expedition with no problems. In fact I averaged 8.4 miles per gallon on our trip from Florida to Illinois. We sold the motorhome and the Expedition and are looking at downsizing. We are looking at a smaller Diesel with a 340 Hp Cummins and 700 Ft Lb of torque. We are looking at towing either a Jeep Gladiator or another Expedition. So will the 700 Ft Lb of Torque be enough to tow the Gladiator 4,650#-5,050# or the Expedition 5,443#-5,692#. I want to be able to tow the best I can to what I have now. I know there are a lot of factors involved here. I just am interested in torque. Will 700 Ft Lb of torque tow 5,000# easily?
Thanks
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Old 07-31-2021, 08:38 AM   #2
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I forgot to mention the new motorhome weights approximately 30,000# or 33,000#
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Old 07-31-2021, 08:59 AM   #3
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Check the torque curve an max torque at what speed an rpm check the spec.on the motorhome four maximum weight towing
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Old 07-31-2021, 09:38 AM   #4
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I now have a motorhome that weights approximately 40,000# and I tow an Expedition that weights approximately 5,700#. Our motorhome has 1,250 Ft Lb of torque and pulls the Expedition with no problems. In fact I averaged 8.4 miles per gallon on our trip from Florida to Illinois. We sold the motorhome and the Expedition and are looking at downsizing. We are looking at a smaller Diesel with a 340 Hp Cummins and 700 Ft Lb of torque. We are looking at towing either a Jeep Gladiator or another Expedition. So will the 700 Ft Lb of Torque be enough to tow the Gladiator 4,650#-5,050# or the Expedition 5,443#-5,692#. I want to be able to tow the best I can to what I have now. I know there are a lot of factors involved here. I just am interested in torque. Will 700 Ft Lb of torque tow 5,000# easily?

Thanks


I also tow a expedition with a limo golf cart behind. My 400hp 1250 torque does well. Going to a little over half the torque I’m sure you will be able to tell the difference.
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Old 07-31-2021, 09:52 AM   #5
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This is a tough question since you have had a higher HP & torque coach… first. If you use you higher numbers. For comparison use 40,000# + 5,700 = 45,700 old coach and 33,000 + 5,700 = 38,700 for the proposed unit. that is 6,000# less or 85% of the weight of your original unit. 700 ft lb of torque is 56% of 1,250 ft lb. Even if you use the lower numbers and lighter vehicle, it is still a big disparity.

It will tow it BUT NOT EASILY. The pedal “feel” will be very different. You are right track to look at torque. Unless you can live with 45% less torque and only lightening the load up 6-8,000 lbs. That is a big spread on paper. I would not make this purchase without towing the Expedition on a couple hour road test. It would be a good shakedown for both the coach and your throttle foot. IMO for similar response to your old coach, I think you would need to be in the 900-1,000 ft lb. range.

Good luck on your choice and let us know how it turns out.
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Old 07-31-2021, 10:37 AM   #6
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You will be able to do it, but I don't think you will like it. -Paul
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Old 07-31-2021, 11:00 AM   #7
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I tow a Toyota Sienna behind our gas class A. Goes down the road just fine.
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Old 07-31-2021, 11:13 AM   #8
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You will be able to do it, but I don't think you will like it. -Paul
Agree... torque makes all the difference. Go for 1000-1100 range at least.
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Old 07-31-2021, 11:22 AM   #9
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I wouldn’t go below 1000ft lb
You will not be happy.
Not many short diesels have a high torque engine.
The Newmar New Aire is the only one I know of, of course it’s probably the best too.
I like the 35 ft New Aire for when I downsize in 10 yrs.
I met a nice gentleman that had one for a year down in Florida last January, he downsized from a London Aire, he loved it.
I can’t see me driving a 43ft when I’m 75. I’m going for a 35 ft in 2030.
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Old 07-31-2021, 11:23 AM   #10
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There will be quite a difference. The weight difference is an important factor, but if you ever watched your "rolling torque" on your previous coach, it used around 500 - 600 pounds of torque to just drive down the road. That leaves 100 - 200 pounds left for a grade.

I had a 2005 Monaco Diplomat that weighed in at 30K and had the 400 ISL (1200 pounds torque). It towed/pulled really well on the grades, losing half that torque would have been huge.

With that said, my current coach, with toad, weighs in at 48K. It has the 450 ISL, but it suffers on the grades. We like the bigger heavier coach and just accept that we'll no longer keep up with some other coaches on big grades. We drop down to 37 - 45 mph on steep grades.

Sooooo.....just remember, grades take up a very small percentage of your drive time. Accept the slower speed and enjoy the view, it will be going by much slower.
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Old 07-31-2021, 11:57 AM   #11
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Just do the math. Your new coach weighs 75 to 80% of what your old one did, but it only has 56% of the torque. You will have about the same wind resistance, so I would guess that you will see a significant difference in hill climbing performance. On the level, you will be fine. Your fuel economy should be better with less weight to move down the road.
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Old 07-31-2021, 12:11 PM   #12
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Originally Posted by 2014Aspire View Post
I now have a motorhome that weights approximately 40,000# and I tow an Expedition that weights approximately 5,700#. Our motorhome has 1,250 Ft Lb of torque and pulls the Expedition with no problems. In fact I averaged 8.4 miles per gallon on our trip from Florida to Illinois. We sold the motorhome and the Expedition and are looking at downsizing. We are looking at a smaller Diesel with a 340 Hp Cummins and 700 Ft Lb of torque. We are looking at towing either a Jeep Gladiator or another Expedition. So will the 700 Ft Lb of Torque be enough to tow the Gladiator 4,650#-5,050# or the Expedition 5,443#-5,692#. I want to be able to tow the best I can to what I have now. I know there are a lot of factors involved here. I just am interested in torque. Will 700 Ft Lb of torque tow 5,000# easily?
Thanks
Most DP's will adhere to the rule of thumb for 10hp/ft with the torque numbers following suit. Towing seems to be automatically figured in.
I have no complaint with ours pulling long 6% grades with it's actual weight being around 32K lbs and the toad weighing in at approx. 4500 lbs.
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Old 07-31-2021, 01:08 PM   #13
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Keep in mind that is the Cummins B6.7 medium-duty engine, the smallest diesel available in a diesel pusher. Coach mfgrs. use it to lower build costs which also lower MSRP. Your previous MH had a heavy-duty engine with another 500 lb/ft of torque.
It is similar to the Cummins B6.7 engine used in a Ram 1T dually.


I know a couple full-timing towing a small SUV, he is not pleased with the performance. On the upside, he gets approx. 10.5 mpg.
tropical36, the formula is actually 1HP per 100LB., at least it has been since I've been a member. Lower than that is considered under-powered
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Old 07-31-2021, 01:37 PM   #14
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Over the years I have always said "it is the torque that counts". However we now have a 33,000 pound motorhome powered by the 340 hp 6.7 liter Cummins. We previously had a 34,000 lb motorhome powered by a 400 hp CAT engine.


What I have learned is that torque is only the predominant factor when both engines are turning over the same rpm. Most diesels are governed between 2200 and 2400 rpm. The little Cummins is governed around 2700 rpm. That is how they get a higher hp with still a low torque. We have been very happy with our "little Cummins". I have to say that I cannot tell a lot of difference climbing hills with our little Cummins than I could with our 400 hp CAT. I can climb a hill at 65 mph in 4th gear thanks to the higher rpm. That makes a lot of difference when you are climbing a steeper hill.


So I say, "try one" you may be pleasantly surprised. If not, then you will know you want the bigger engine.
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