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5th wheel mount on 12ft flatbed Class 4 Ford F450 Dual with New 7.3 Diesel


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First time RVer. Old mechanic. (late 60's)

I have a 2001 Ford F450 Super Duty (15,000 GVWR) and to put the 5th wheel hitch in the center of the rear axle is a full 6 ft from the rear of the flatbed.  So placing the hitch with some clearance would require a full 2ft behind the axle. going to pull a 28ft Carri-Lite, 8500lb dry weight and 1450lb hitch weight. 

100% not afraid of cutting off the rear of the flatbed and notching the corners for clearance to keep it below 1ft, but wondering if I am over compensating. A LOT of truck for a little 5th wheel.

Ideas? Realistic experiences? Am I being too cautious, or just weld on a 5th wheel hitch and see how it pulls and check what the weight balance is? 

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With that large of a truck and that light of a trailer, I'd just mount the hitch behind the axle where the trailer clears the rear of the flatbed.  You can see how much the truck will squat or lift the front end by putting 1500 lbs of a load at that location - maybe lower the trailer's hitch pin onto a metal plate to spread the load on the bed.

People tow conventional trailers with the hitch point behind the rear bumper so you shouldn't have any trouble towing a light 5th wheel with the pin slightly behind the rear axle.

Edited by Lou Schneider
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I think you will end up moving it forward.  I have a 2002 f450 165 wb 84in CA.  Struggled with this as well. ended up ditching my original flatbed for a northstar model designed for this chassis. The gooseneck ball is 2 inches ahead of the rear axle. The flatbed is mounted with a 2 inch gap between the cab and bed. the corners are angled off but not a lot. When it sits next to my f250 long bed with a bw turn over ball hitch. measures basically the same from the ball to the end of the tailgate with it down. They know you will have to back under with the tailgate down so i am hoping the clearance will be enough. I have not purchased a toy hauler yet. I have measured a few and don't believe I will have a problem. everyone says pin weight is 20 percent of total weight,  tongue weight is less as almost all the weight of the trailer is on the trailer axles.  I don't think it would be unsafe or overly squirrely but I'm no expert. probably look kind of goofy

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I've driven behind a truck/toyhauler combo with not enough hitch weight.  Scary stuff.  Truck was Volvo 770.

Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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A stick is what you need. Use it to measure "swing clearance". 

Make it as long as the distance from the closest point on the front of the trailer to the king pin. Lots of trailers have sloping fronts behind the tow vehicle. Measure up high on that to get your closest distance. 

Take your accurate stick to the proposed tow vehicle and place one end on the centerline where you would like the king pin to be connected. 

Swing said stick to 90 degrees each side.

The rear corners are the usual points of trouble. Measure to what sticks out the farthest. 

If it clears all parts of the vehicle by 4 inches you are good. 

If it does not you need to move rearward until you have the 4 inches.

Then look at "dip clearance". This is the clearance for the tow vehicle and trailer not to come in contact as the rig travels through "dips". It is vertical clearance.

With a flatbed body this should not be any issue with a RV 5th wheel coupled trailer as they are primarily designed to be towed by pickup trucks. 

If you end up having to locate the king pin behind the rear axle, then refer to your truck's rear hitch ratings vs it's 5th wheel hitched ratings.  Especially as you go farther back. 

What you want to avoid is 3000lbs of hitch weight at the rear of a truck rated for 2000 on the rear hitch.  Their is no way to "weight distribute" weight to the trailer axles and steer axle via a 5th wheel connection like you can with a weight distributing rear hitch. 

Part 2 is make a stick as long as the distance from trailer king pin to it's front corner.  Most RV trailers have "zero pin offset" meaning the pin sticks out even or a bit ahead of the front of the trailer. 

Use this stick to check clearances from the hitch point you discovered above ^ to anything you may intend to mount on the bed ahead of the trailer.  This is "jacknife clearance". 

Then X marks the spot. 

Now if your trailer king pin weight is 1200 lbs and your truck is good for 2000 on a rear hitch no weight distribution put your hitch wherever you want ignore above blah blah blah. 




"Are we there yet?" asked no motorcycle rider, ever. 


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