kehyler

In the 2018 owners manual (link here), it states on page 291 under “RECOMMENDED TOWING WEIGHTS” is “Note: For high altitude operation, reduce the gross combined weight by 2% per 1000 ft (300 m) starting at the 1000 ft (300 m) elevation point.” Does that mean that that I could be legally overweight at the top of, for instance, the ike gauntlet with a load that I was not legally overweight at the bottom?

Thanks!

smokeywren

There's nothing "legal" about the GCWR. It is simply a guideline that tells you the max weight your rig can weigh without overheating anything in the drivetrain, and without being the slowpoke holding up traffic on steep grades. But yeah, the engineers test the GCWR at about 1000 feet altitude, so when towing at higher elevations you won't have as much power and torque to climb the grade, and as always you must pay attention to your gauges, especially the tranny temp gauge.

And BTW, the GCWR (and tow rating) is not the limiter as to how heavy a trailer you can tow without being overloaded. GCWR ignores payload capacity, and payload capacity of the tow vehicle is usually the limiter. Assuming your receiver with WD hitch is not your limiter, then the probable limiter is payload capacity available for hitch weight.

Payload capacity available for hitch weight = GVWR (not GCWR) of the tow vehicle minus the wet and loaded weight of the tow vehicle ready to tow. "Wet" means full of gas, and "loaded" means including everybody and everything that will be in the tow vehicle when towing, including pets, options such as cab steps and moon roof, accessories such as a bed rug and camper shell, toolbox with tools, jack(s), campfire wood, grill and fuel for the grill, toys such as bicycles or dirt bikes, everything. Yes, you must weigh the wet and loaded tow vehicle to determine payload capacity available for hitch weight.

Subtract 100 pounds for the weight of a good WD hitch from the payload capacity available for hitch weight, and the answer is the payload capacity available for tongue weight.

Divide the payload capacity available for tongue weight by 0.13 (13%) and the answer is a rough estimate of the max weight of any tandem-axle trailer you can tow without being overloaded. If you're smart, you'll use the GVWR of the trailer as the max trailer weight.

kehyler

Thanks for the notes about payload (though I'll admit to knowing about them beforehand).

Couldn't it be considered "negligent driving" to tow outside manufactured limits?

smokeywren

Yes, if you are involved in an accident where someone gets hurt, then the other driver could sue you for negligent driving, and probably win the lawsuit. But if you get close to the GCWR of your tow vehicle, you're going to be way overloaded over the GVWR and payload capacity. The lawyers won't sue you because you exceeded the pulling power of your drivetrain, but because you were overloaded over the payload capacity of your tow vehicle. So don't worry about GCWR and tow rating, Instead concentrate on GVWR and payload capacity. If you don't exceed the GVWR of the tow vehicle, then you won't exceed the GCWR either.

kehyler

Thanks for the advice, which is generally true, but for certain trucks (XLs and XLTs with few options except the payload packages), it is possible to exceed the GCWR before the GVWR. It is especially possible to do so with the 2% GCWR reduction factored in from the Ford Manual. Note that it does not say to reduce the GVWR.

mass-hole

I've notice that too and I am not really sure why its there with the Ecoboost trucks other than maybe a overheat thing. They clearly have the power at any altitude. TFLtruck pulled 12k lbs up the Ike Gaunlet like it was nothing and that peaks at 11,000 ft. You'd have to reduce GCWR by 22%!

kehyler

Yeah, it's a huge reduction in capacity.

acdii

It's for performance reasons only. Your truck doesn't magically lose carrying ability going up a mountain, but engine performance does suffer, the EB can overheat at high altitudes pulling the max weight(been there, done that), and the 5.0 loses power as it climbs. Its a Protect Ford clause, lawyerease, keep the GP from suing clause.