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Old 07-19-2014, 11:43 PM   #1
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Pinbox and hitch issues

After more than 6 months and numerous hours of dedicated research we’ve narrowed our choice of 5th wheels and tow vehicles to a very short list. My main concern now is verifying compatibility between the two before we pull the trigger.

Is there a standard height for the kingpin and the hitch? Are most pinboxes adjustable? Are hitches adjustable when mounted in the truck bed? Will any kingpin fit into any hitch receiver (provided the vertical alignment is good)? I need to be sure if I buy a 4x4 that sits high off the ground that the hitch and/or kingpin will have a range of adjustments so that they can align with each other.

Also, should I look for a pinbox or hitch with some sort of shock-absorbing qualities to mitigate the bumpy, jerky ride over rough terrain? Which type works best?
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Old 07-20-2014, 12:39 AM   #2
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No standard height for pin box that I'm aware of.
I had 4, 5ers and they were all different.
Each 5er had 6" in 2" increments ( 3 positions )of pin box adjustments. Lock tight the bolts if you make this adjustment.
I had the same brand of hitch in both my TV's and it had 8" of height adjustment.
Pin and hitches are an industry standard size. But you need to match the hitch to the trailer weight. Not all hitches have the same capacity.
You will have to be good with a tape measure to be sure the truck height and adjustments available will give you the box top rail clearance necessary 6" minimum.
Most newer 5ers will adjust to a stock height 4X4. Both my TVs were 4X4. Oversize tires reduce the pulling capability and can over work the transmission when towing near the trucks limits.
JMHO: A raised 4x4 is not good for towing; and raising a 5er to match a raised truck can produce a whole pile of handling issues as the center of gravity goes up.
I didn't have shock absorbing hitch or pin box, don't now if any have been tested for off road use
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Old 07-20-2014, 08:19 AM   #3
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Yes, there is an industry standard "range" for the height of the pin box. The actual height varies by several inches within that range.
Yes, almost all pin boxes and hitches have some height adjustment, since there is no standard on the height of a pickup bed.
Yes, the pin size and hitch jaw size are standardized. There are several different types & designs for the jaws, but they are all based on the same pin size for RV applications.

Its somewhat a personal preference choice, but yes, in my opinion either an air pinbox or an air ride 5th wheel hitch significantly reduce the chucking transfer from the RV to the truck. The air ride hitches are very expensive and mostly intended for very heavy rigs. I use the TrailAir brand air pinbox on both my 5'ers, but there are several manufacturers of good quality air pin boxes and air hitches.
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Old 07-20-2014, 11:39 AM   #4
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Industry standard for pin height is 46-48 inches for pin height. And generally the standard drop height is 12 inches (but the pin box can be lowered which will raise the front of the fiver). So, the underside of the fiver will be around 60 inches. Recommended clearance between the fiver and top of the truck bed rails is a minimum of 6 inches. Depending on truck suspension and fiver pin weight, the truck will sag 1-2 inches.

What all this means roughly is if your solo truck has a bed height of more that about 56 inches, then the fiver will not tow level. But since the pin box is adjustable and most standard hitches are also adjustable, you can achieve the required clearance. Just depends on how out of level the combo will be. Some trucks can be lowered, especially 4x4s by removing or replacing rear axle spacer blocks. Finally, the fiver can be raised. Some fivers have spring hangers that are adjustable to raise the trailer, otherwise spacer blocks and longer U-bolts will also raise the trailer. Both methods put greater lateral stress on the trailer suspension. The better and more expensive solution is to torch off the spring hangers and add a sub frame under the frame rails with new spring hangers.
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Old 07-20-2014, 12:39 PM   #5
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I'm lovin' this forum! The insight gained from the experience of others is sure to help me make better, more informed decisions in my quest for the ideal truck and trailer. With so much money on the line, I'm grateful for your shared knowledge. Thanks for the replies, guys.
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Old 07-20-2014, 01:07 PM   #6
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If you are interested in fords, their 4x4 and 2x4 bed heights are usually the same height.
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Old 07-22-2014, 02:03 PM   #7
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If you are interested in fords, their 4x4 and 2x4 bed heights are usually the same height.
Specs sheet for my 2013 F250, bed height 4x2=34.1 inches, 4x4=35 inches. F350, 4x2 = 33.8 inches, 4x4=37.8 inches. Big difference on F350, not much on F250.
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Old 07-22-2014, 07:42 PM   #8
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It seems like the newer trucks, about 2010 +/- and up, have higher bedsides, which can make optimum adjustments for a 5th wheel tricky. Not sure why they did that, but I've sure read about lots of problems when someone has their 5th wheel trailer set up just right and then gets a newer truck and can't get enough clearance on the bedrails.
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Old 07-23-2014, 09:29 AM   #9
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JMHO: A raised 4x4 is not good for towing; and raising a 5er to match a raised truck can produce a whole pile of handling issues as the center of gravity goes up.
This is 100% incorrect and unless you modify your truck with like a 4 to 6 inch lift kit you won't have to adjust anything on the trailer. Also I wouldn't recommend towing with anything other than a 4x4 if you plan on ever leaving pavement. A little wet grass on a hill can make you stuck and even if you only use it once you will be glad you have it, lol!

I live in ND and they don't even sell 2 wheel drive trucks here so I might be a little bias, but I'll never have a 2wd one for pulling a trailer I can tell you that! I've used 4x4 on many occasions going in or out of campsites with dirt roads after a rain.
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Old 07-23-2014, 12:38 PM   #10
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JMHO: A raised 4x4 is not good for towing; and raising a 5er to match a raised truck can produce a whole pile of handling issues as the center of gravity goes up.

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This is 100% incorrect and unless you modify your truck with like a 4 to 6 inch lift kit you won't have to adjust anything on the trailer. Also I wouldn't recommend towing with anything other than a 4x4 if you plan on ever leaving pavement. A little wet grass on a hill can make you stuck and even if you only use it once you will be glad you have it, lol!
Maybe you missed the word "raised" just before 4x4 in the earlier post which means a lift kit. So Skip426 is 100% correct in what he stated and you are really in agreement. Just about all of today's trucks, 2wd or 4wd have bed heights above 56 inches and will result in the fiver being nose high.

My experience is a little different, never stuck on or off pavement in 26 yrs of towing and never owned a 4x4.
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Old 07-23-2014, 01:39 PM   #11
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My bad, ya I guess I missed the part where the op talked about getting one high enough and thought skip meant the couple inches difference in height that 2wd vs 4wd used to be would cause an issue. I apologize. If he was referring to a lift kit then he is 100 correct and I agree, however I still think 4x4 is best, it's essential where I live and drive but everyone's needs will vary. Used 2wd are cheap around here cause you can only drive them half the year and 4x4 hold value very well.
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Old 07-23-2014, 11:06 PM   #12
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I realize now that I need to choose my words more carefully so that I’m not misunderstood. When I said in my original post “if I buy a 4x4 that sits high off the ground…” I didn’t mean I wanted it to sit high off the ground, and certainly not raised with a lift kit higher than it already is. I was simply trying to determine what range and type of adjustments were typically available to accommodate trucks of different heights.
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Old 07-23-2014, 11:20 PM   #13
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If you get a taller truck the hitch can be adjusted but not the box. I believe you can max out the box sides so towing is difficult. On my 5er the max box height is 56". Unfortunately that only gives me about 5 inches of clearance. Have upon occasion rubbed the top of the box with the underside of the trailer. Fortunately not too much damage. Makes me very cautious.
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Old 07-24-2014, 02:45 PM   #14
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I realize now that I need to choose my words more carefully so that I’m not misunderstood. When I said in my original post “if I buy a 4x4 that sits high off the ground…” I didn’t mean I wanted it to sit high off the ground, and certainly not raised with a lift kit higher than it already is. I was simply trying to determine what range and type of adjustments were typically available to accommodate trucks of different heights.
As Gordon has confirmed, once the truck bed height hits about 56 inches, you will either loose critical clearance between the truck bed and the fiver overhang or be forced to tow with the fiver nose high. In reality, being a few inches out of level will make little difference in towing characteristics or your living/sleeping comfort if you remain hitched while camping. But being nose high does put more weight on the fiver's rear axle, reduces fiver suspension travel and creates more risk of tail dragging.
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