f150 enough?
02-11-2015, 12:12 PM
#21
Senior Member
That's true for payload capacity, which is GVWR minus the weight of the truck.
But it's not true for GCWR and tow rating. Tow rating is GCWR minus the weight of the truck. But GCWR depends on engine and axle ratio, as well as options that can cause the truck to weigh more or less, such as 4X4 or 4x2, cab, and bed length. Change the axle ratio and you change the GCWR (and tow rating) of the truck.
2012 F-150 4x2 SuperCrew 5.0L with short bed and 3.31 or 3.55 axle has GCWR of 13,500 and tow rating of 8,000. Same exact truck but with 3.73 axle has GVWR of 14,900 and tow rating of 9,400. So replacing the ring gear and pinion with 3.73 ratio would gain you 1,400 pounds of GCWR and tow rating
Those tow ratings are valid only when the wet and loaded truck with people, stuff, full tank of gas, and weight-distributing or fifth wheel hitch grosses less than 5,500 pounds before you tie onto the trailer. So don't think for a second that you can actually tow a 9,000-pound trailer without being overloaded. But you'll be overloaded because of GVWR that limits hitch weight, not GCWR that limits gross trailer weight.
IOW, payload capacity, not tow rating, is still your limiter as to how heavy a trailer you can tow without being overloaded.
So if you feel like your truck needs a little more power to muscle a trailer up the pass, then changing the ring gear and pinion to a 3.73 ratio will definitely give you the feel of more muscle for towing that trailer up the grade. But if you're overloaded over the GVWR of your truck, there's nothing you can do to fix the problem except tow a lighter trailer or trade for a heavier-duty truck.
But it's not true for GCWR and tow rating. Tow rating is GCWR minus the weight of the truck. But GCWR depends on engine and axle ratio, as well as options that can cause the truck to weigh more or less, such as 4X4 or 4x2, cab, and bed length. Change the axle ratio and you change the GCWR (and tow rating) of the truck.
2012 F-150 4x2 SuperCrew 5.0L with short bed and 3.31 or 3.55 axle has GCWR of 13,500 and tow rating of 8,000. Same exact truck but with 3.73 axle has GVWR of 14,900 and tow rating of 9,400. So replacing the ring gear and pinion with 3.73 ratio would gain you 1,400 pounds of GCWR and tow rating
Those tow ratings are valid only when the wet and loaded truck with people, stuff, full tank of gas, and weight-distributing or fifth wheel hitch grosses less than 5,500 pounds before you tie onto the trailer. So don't think for a second that you can actually tow a 9,000-pound trailer without being overloaded. But you'll be overloaded because of GVWR that limits hitch weight, not GCWR that limits gross trailer weight.
IOW, payload capacity, not tow rating, is still your limiter as to how heavy a trailer you can tow without being overloaded.
So if you feel like your truck needs a little more power to muscle a trailer up the pass, then changing the ring gear and pinion to a 3.73 ratio will definitely give you the feel of more muscle for towing that trailer up the grade. But if you're overloaded over the GVWR of your truck, there's nothing you can do to fix the problem except tow a lighter trailer or trade for a heavier-duty truck.
SMOKEY... clarify this for me please.
I was under the impression, much like payload capacity, that the rating of the truck from the factory does not change, regardless of what modifications you do to it. Just like adding airbags will increase your "ability" to carry more weight better, but will not increase the rated payload of the truck on the doorjamb sticker.
I believe (correct me if I'm wrong) you're saying that the payload and gvwr will end up being the limiting factor on the towing. I agree with that. But if changing the gear ratio will increase his "legal" tow rating, why does adding a leaf spring or airbags not increase his payload or gvwr? (which I understand it doesn't.)
These are questions I ask because I want your take on it. Not because I disagree with you. Trying to educate myself
02-11-2015, 06:37 PM
#22
Grumpy Old Man
There is no "legal" tow rating, which is GCWR minus truck weight. The GCWR is an advisory limit that tells you the gross weight your drivetrain can pull without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
If you study the Ford RV and trailer towing guide (or your Owner's Guide), you will see the things that make up the tow rating. Engine power and torque being the most important, but the leverage of your final drive ratio being important too. You won't find the GCWR on the truck - just in the Owner's Guide where it tells you how to determine your GCWR (and tow rating) based on engine, transmission, options that make up the weight of the truck, and axle ratio. You cannot easily change the cab or engine/tranny or 4x4/4x2, but you can choose your axle ratio. If you don't like your 3.55, then replace it with a 3.73 and gain GCWR and tow rating. And it's completely "legal" because it's in your Owner's Guide.
GVWR (and payload rating) is another ball game. The GVWR is on the Federal Certification Label in your doorframe, and it won't change just because you changed tires, wheels, shocks, springs or other components that determine payload capacity.
If you exceed the GCWR, you might overheat something in your drivetrain and burn up your engine, tranny, or differential, and you'll definitely notice a lack of performance when towing up steep grades. But you're not much danger to others on the road. A burned up tranny will usually give you some warning before it quits completely.
But if you exceed the GVWR or payload capacity, you're in danger of breaking something such as springs, shocks, wheels, frame, axle shaft, etc. Those broken parts at highway speeds could cause you to lose control of the truck and trailer and definitely endanger those sharing the road with you.
The following users liked this post:
driver444 (02-12-2015)
02-11-2015, 10:15 PM
#23
ok, my gcwr is 13500 and I should be somewhere around 12265, so that should be ok. My payload, after weighing my truck at 5820, is around 1230 and my hitch is wd1100. tongue weight should be 970, so that should be ok my tow rating was 8400# and the trailer is around 6300#loaded so that should be good. The change in gearing should help my giddy up and go.
02-12-2015, 06:35 AM
#24
Grumpy Old Man
That's an estimate. After you have the rig wet and loaded and hooked up with the spring bars tight, then weigh it on a CAT scale. Add the weights on the front and rear axles of the tow vehicle and compare the total to the GVWR of the pickup. Then you'll have facts, not estimates.
02-12-2015, 07:16 AM
#25
hey smokewren, so far all the advice you given has been very helpful. I listed all the numbers that I had so far so that I don't purchase a trailer that I can't tow and then have to buy a different tow vehicle.
