# Truck towing capacity: Weight Vs. Drag

#### strantor

Joined Oct 3, 2010
5,225
I have the 5.3L Vortec, but rated at 240HP.
You have a Chevy engine in a Ford van?

#### BR-549

Joined Sep 22, 2013
4,938
I’ve pulled flatbed doubles, 1 ton square bales. Single cab, no flare. Hay is not a smooth surface.

Have never experience increased fuel cost like that.

That’s my long ago experience. Maybe it’s the fuel nowadays.

#### Papabravo

Joined Feb 24, 2006
12,944
The guys who do miles per gallon over a fixed course use rock hard bald tires to minimize both static and rolling friction. Underinflated tires could produce the results you are seeing.

#### Brownout

Joined Jan 10, 2012
2,390
You have a Chevy engine in a Ford van?
No, I meant to say 5.4L Triton (ford)

#### tcmtech

Joined Nov 4, 2013
2,868
Towing capacity is typically factored against a vehicle's braking capacity and total mass.

That said some years ago I had a 85 Ford f150 that I refitted with a built up 460 that would do ~400 Hp and 500+ ft/lbs of torque with a built up E4OD behind that.

Towing anything regardless of weight or wind drag was never a problem!
(But slowing down fast without engine braking could be at times.)

Towing a 20' enclosed trailer with a 8' x8' flat front face at 75 MPH into a 40+ MPH head wind was doable just not in overdrive.

#### GopherT

Joined Nov 23, 2012
8,012
If I were to install a load cell in my trailer hitch and feather my accelerator to keep the readout always below 8,000lbs*, I theorize that I could probably pull massive amounts of weight, with very slow acceleration and limited highway speed (assuming the trailer had brakes capable of stopping its own load). I theorize that on flat roads, I could probably pull even more still. I theorize that the manufacturer's towing capacity rating is just a "shoot from the hip" guesstimate and really isn't real-life applicable.

So why is wind drag and incline excluded from manufacturer's documentation and why does nobody talk about it? Aside from retrofitting my trailer hitch with a load cell, how can I calculate the load my truck is actually able to pull, given the frontal area of the trailer?
You should have bought a Toyota. Also, do the math on the potential energy for every 6-foot hill you go over. Momentum doesn't carry over from down hill to the next up-grade so you are essentially asking that little engine to lift the entire mass of you, truck, trailer, payload and on and on each time you go up a hill. So, any kinetic energy your do have, 0.5 * mass * velocity)squared gets sucked up as potential energy and your velocity quickly decreases.

Wind depends on a lot of things but the hills will kill you as well. Not exactly hills in your area but overpasses and the 6-foot undulations do the same damage to mpg, average speed and la, la, la.

You were right though. See toyota on flat, slow acceleration, ...

#### strantor

Joined Oct 3, 2010
5,225
You should have bought a Toyota.
Oh, trust me, I would love to have one. That "new" ('07+) tundra is a really nice and good looking truck. Before I started truck shopping (looking at ) it was my #1 pick. But Toyota's resale value is so good that I couldn't even afford to get into an 8y/o truck! But it's OK, I'm perfectly happy with the '05 GMC I got. The MPG I get in the truck without a trailer more than makes up for the lackluster towing performance. I can get 20MPG driving around 70+mph and accelerating like I'm on a mission. If I really want to stretch the gas, I can keep it under 65 and drive like a codger with the A/C off, drafting big rigs when convenient, and like I said earlier, I can average 27MPG over a whole tank of gas. I have two coworkers that drive the new Tundras and they both tell me that no matter how they drive, they never get over 15MPG. I would however like to drive one for a week and see what kind of MPG I can get out of it. Driving a Prius for over a year kinda reprogrammed my foot; maybe just a complex, but I feel pretty confident that I can get better MPG than most people, out any given vehicle, without causing any noticeable delay in my travel time.

But, if in the future I ever need a trailer puller, I'm getting one of the older ford duallys (duallies?) with the 7.3L powerstroke turbo diesel. I drove one of those in high school and it's beast! I don't think there's anything it couldn't pull, and pull faster than it should.

#### Brownout

Joined Jan 10, 2012
2,390
But, if in the future I ever need a trailer puller, I'm getting one of the older ford duallys (duallies?) with the 7.3L powerstroke turbo diesel. I drove one of those in high school and it's beast! I don't think there's anything it couldn't pull, and pull faster than it should.
I'm still shopping for a truck that can pull my 11,000 # trailer and haul a few more creature comforts. The van in the picture (if you remember from earlier) is over matched by the trailer, although it pulled it >1,000 mi from Alabama to Minnesota last summer. It's not so much that it's underpowered, but more of a control thing when I'm being passed by a semi and get blown around like a toy. Also, the van is loaded to the max, and no margin for any more cargo, which would be nice to have on my long contract jobs away from home.

The one I'm looking at now has the 7.3 PS. It's a 1996 International D4700. It's a two-ton truck. Many RV's are moving up to the two-ton class lately.

#### Lestraveled

Joined May 19, 2014
1,946
Chevy Duramax diesel with the Alison Transmission. The trans and engine work great together. Going down hill, tap the brakes twice and the transmission down shifts to hold the speed. My wife loves it. She puts her sunglasses on, plugs her music in, and will drive our rig (32' fifth wheel with a 14' buggy trailer behind) like a pro, while I take a nap.

#### Brownout

Joined Jan 10, 2012
2,390
It's nice to be able to triple tow. Wish I could do that on my winter runs from Alabama to the Gulf Coast, so I could tow my boat. It's not allowed in Alabama or Florida though.