Ok so I have a 2016 Scab 4x4 2.7. According to the door sticker my max payload is 1682lb. According to the gawr (6800lb) I could 'safely' increase the payload to around 2000lb with proper tires and suspension. Assuming that is true(lt tires and extra leaf to handle beyond that amount) I'm reading tha the limitation is the axle (3.55 gears. 8.8). But I'm thinking why is the axle the limiting factor? Max tow is around 10,000 lbs, and to me that puts much more stress on the axle than 2000 lb. Can anyone explain why payload is more limited than towing weight?

My dilemma is this. I plan to buy a popup slide in camper weighing around 1700lb. Adding me and all my gear I willprobably exceed the 2000lb max axle load (6800lb gawr - 4800lb truck weight) even with the lt tires and extra leaf. I have carried over 2000llb in my old 90 f150, which had the 9" rear and it did fine. I honestly don't know how these 8.8" axles compare.

Any thoughts much appreciated. Fwiw I am currently towing a 1500lb popup with no issues whatsowver.

 

Problem with half tons is the payload will be your limiting factor when towing. Sure it will tow 10k easily but legally not so much. These tow numbers for 150 are marketing and that's it if you ask me

 

But I thought max tow is based on gcwr? And that's what I think the DOT uses when they weigh you? My gcwr is somewhere over 14,000lb I don't have the exact number. Which makes my max tow somewhere around 9500-10000lb.

Can you explain about the non legal part? Very curious, maybe something I've missed.

 

Max tow trucks have the 9.75 axle so its not a straight across comparison to your 8.8 truck.

Max tow also isn't the same as payload. The tow rating is only how heavy the trailer can be. In a nutshell, its what the power train can pull and still cool itslef. Brakes and whatnot also come in to it.

There was a time that max tow also increased payload, but that went by the wayside in 2015.

You're talking slide in camper. The towing ratings aren't really a factor here. It's payload.

If you're over, you're over.

Now, that's by the ratings. You can get more in it and and you can get it moving. It may sway more, it may have longer stopping distances or it may sit low. It may damage or wear out components faster over the long haul.

But if you're over the gvwr and get wieghed, you're going to get dinged by what the truck is rated for, regardless of what you've done to it in an attempt to increase payload.

Gvwr is what it is and Johnny law isn't going to care about tires and overloader springs....

 

From Ford webpage:

Gross Axle Weight Rating (GAWR) is determined by the rated capacity of the minimum component of the axle system (axle, computer-selected springs, wheels, tires) of a specific vehicle. Front and rear GAWRs will, in all cases, sum to a number equal to or greater than the GVWR for the particular vehicle. Maximum loaded vehicle (including passengers, equipment and payload) cannot exceed the GVWR.

 

Actually your 90 would have most likely also had the 8.8. The last year of the 9" in a truck was 86. The newer 8.8 (15+) are much stronger than the old ones so it's not likely the diff is the limiting factor. Either way as was said above even if you modify the truck to handle more payload the law still will not see it that way. If you want to do it legally you need more truck.

 

Apologies, when I said max tow I meant max towing weight for my truck. Which I just looked up and it's 7600lb not over 9500lb like I thought.

Regardless, yes, to the law the gvwr is what it is. But honestly I'm really not that worried about being weighed. I am worried only about being reasonably safe. In my case I will take care of the suspension and tires, the only concern was the strength of the axles.

I could've sworn the 90 had 9 inch axles, but this was many years ago so my memory is not that reliable. But it is encouraging to know that the newer axles are stronger. If that old workhorse could do it, this 700lb lighter horse should be able to no problem.

Another thing that was brought up is brakes. That shouldn't be a problem, currently I don't see much increase at all in stopping distance with my popup. Haven't taken if on steep grades though just up and down hills. Tow mode downshifts are really nice.

 

The problem isnt being weighed-its that if you are ever in an accident you will likely be found at fault, could be cited/prosecuted, and potentially sued.

Your camper is quite simply too much for your truck.

 

It's your haul, But I would personally have more truck. It must be a very small slide in if it only weighs 1700 lbs.

You seem a bit fixed on the 8.8 axle being limiting factor, but it's more than that. Tires, wheels, suspension, braking, cooling, gearing, etc. It all comes into play for GVWR. Lets also not forget that slide in is going to increase your frontal area, which is also going to effect how it hauls. For example: cooling could become a factor as more frontal means more power, which means the engine/transmission are working harder and making more heat, where more cooling would be a welcome addition. even if it only sticks up 6" above the cab and 2-3" out on either side, that's a fairly large increase in frontal area. There's also a drag penalty you are going to pay for that tall flat surface at the rear of the vehicle. It all factors in to how hard the drivetrain has to work (and cool).

Overloading your RAWR can cause sway, extended braking (over GVWR) or in worse case scenario; bent or damaged components.

The "stronger" 8.8 supposedly is similar to the 8.8 that came in the mid 90's explorers and later f-150's. The ring gear is only as strong as it have ever been, an 8.8 gear is 8.8 gear. improvements were: 31 spline axles (vs 28 spline) larger wheel bearings and thicker tubes. The 31 spline axles also lead to a slightly increased pin diameter int eh carrier, but that's about it.

But don't construe that to mean it's strong enough to take over it's RAWR and not have issues at some point. You're mainly concerned with the ability of the axle to resist deflection (in static and dynamic loading) when talking only abou the axle assembly itself. The 8.8 tubes are still not what I would call "robust". You can bend them being overloaded and hitting a good bump (ie: Dynamic loading is exponentially higher than static). I've seen negative camber on them before from such issues and it's almost always a bent tube. There's a reason high hp mustangs and offroaders brace the tubes to the center section. I've had my 300 hp fox mustang spin a tube before on a hard launch. The plug weld they use to attach the tube to the center section is a very weak point. That's hp related, which won't/shouldn't be a problem for you. I'm not sure how the "new" 8.8's are built in this regard.

I also believe they are still "c" clip axles. Meaning: if you break and axle shaft, the tire is departing. That's bad JU-Ju at highway speed. Not a likely scenario, but I've seen it happen from both high HP (drag racing), shock loading (IE: offroad) and just general metal fatigue. Those were all 28 spline axles though, the 31 spline is supposed to have approx 33% more strength rating.

Using your numbers; 4800 + 1700 = 6500. Truck is 6800 GVWR. You are already within 300 lbs and you're not in it and nothing is in the truck.

Now, if you're using "published weights" for your slide in, you can probably add about 500 lbs to that. Manufacturers do some sneaky stuff when they weigh these things. They will weigh a base model with nearly nothing in it. Like they may not have batteries, or propane tanks, etc. water is never weighed, be it black, grey or fresh tanks and water builds up weight fast. Some will actually weigh without ovens or fridges as they can change manufacturers or they are a customer select-able option. But lets assume these only a 200-300 lb difference. That puts you within 100-200 of your GVWR.

Going to take clothes? food? beer? chairs? hoses? dogs? a friend? etc?

The friend is particularity important because that means more food, more clothes, more beer.....

It ads up quick.

Hauling a 1500 lb trailer is not comparable to a 1700 lb slide in. The slide in places much more stress on the truck's components. I haul a 9000lb trailer with my 2016 truck but I am well under my GVWR when loaded. Grossly under the towed trailer weight and GCWR. But I also bought my truck to do what I wanted it to (max tow optioned lariat Super crew).

OEM's also know that some people are going to overload their trucks. They can't control that once it drives off the lot. Do they build in a "safety factor" in their weights? I like to think so, but they'll never state that, they stick to their numbers. Those numbers are where they tested to. Anything over the numbers is going to be a compromise somewhere with what has been accepted/legislated as safe: control, handling, braking, longevity, etc. What are those exact effects? They're also not going to specifically tell you that either. Legal obligations and whatnot.

I'm not trying to be the weight police on you here, I don't like that sort of thing like anyone else. But you are trying to justify being overweight when it's not justifiable. There's just no way to justify it by the numbers. The OEM has given you the tested ratings, anything else is just an opinion or assumption.

A guy can talk himself into doing anything if he wants to, but numbers are an absolute. If you're going to do it then just do it and be happy with your choice. But it's not a wise move. You may never have a problem, or you may have to make an emergency maneuver and have the truck lean way over and not respond they way it should and end up over the curb and on top of someones kid....

Make sure you drive reserved and when/if something breaks just chalk it up to the cost of being outside the specs.

But slide ins really are the territory of 250 and 350 trucks. Use d to be even 250's had to have the "slide in camper" option package (used to be called "camper special" for most OEM's), mainly to handle the weight.

You might get away with an f-150 with the heavy duty payload package, but that's an OEM option change and your truck doesn't have that...yours sounds like its optioned like a basic "commuter" style vehicle and weekend hauling yard type stuff.

Sorry that was so long, but there's a lot of points you're asking about here and it's not as simple a subject as most think...

 

You cannot increase payload. Period. That camper is beyond the capability of your truck.