fifth wheel hitch

Yesterday I changed out my Trailair pin box on my Mobile Suites 36 TK3 with a MORryde rubber pin box. The short test ride afterward showed dramatic improvement, no more violent chucking, bad enough to lock up my seat belts.
I am also pleased with the outcome because:

• I now have a pin box that can absorb some chucking without actually causing chucking
• No more fiddling with air pressures in an air bag that has warnings about overinflation
• Less prone to rusting, I discovered a pocket with no drain holes on top of the Trailair that is rusting

Here is a photo of the rusting area:

Curt 25K shown below. I can see the height from pivot point to top of hitch plate is several inches. The B&W pivot point is right at the king pin level and would not exaggerate what you are talking about. Sounds like you should sell the curt and get a B&W.

Cummins12V98,
Yes, I agree the chucking is coming from the hitch, but the motion of the hitch head is caused by angle change of the Trailair pin box lower jaw. The hitch head cannot move indepently of the pin box. Try holding a 12 ruler with one end resting on a table, hold the other end at a 45 degree angle to the table, let the end you are holding drop down 1 inch. You will observe the end resting on the table move away from the end you are holding by 1 inch. Why 12 inches, because the horizontal distance from the pin is 8.5 inches and the vertical distance from the jaw pivot point to the head pivot point is also 8.5 inches creating a 45 degree right triangle with an hypotenuse of about 12 inches. So when the pin box moves up 1 inch relative to the truck, the hitch head pivot point is jerked back 1 inch and vice versa. I have no problem with the design intent of either the Trailair pin box or the Curt hitch, it's just that they don't work well together. This system problem would not be as pronounced with other combinations. For example, the Trailair and the B&W Champion with a head pivot point just below the hitch head surface. Another example the Curt hitch with a Flex Air pin box with a second pivot point in the lower jaw.

Sezzell, I towed a 2007.5 36' Mobile Suites with the TrailAire air bag pin box with ZERO effect from the lower jaw moving up and down. It it were a AirBorne I could see this to a small degree because of its short distance from pin to pivot point. The TA has a much longer distance from pin to pivot point and would cause virtually no fore and aft movement.

I think if you have any fore and aft movement it would be coming from your CURT hitch not the pin box.

What air pressure are you running in your truck tires?

Take some time to consider how both the hitch and the trailer pin box system work together. I say this based on my experience with a Ram OEM hitch actually manufactured by Curt on my 2016 Ram 3500 and a Trailair pin box on my 2006 Mobile Suites 36TK3. The Trailair pin box has a pinned lower jaw that is free to rotate. A pneumatic spring and shock absorber control the vertical motion of the Trailair's lower jaw. This design is supposed to reduce rough road shock from being transmitted from the hitch to the trailer. However, as the jaw pivots like a scissor opening and closing, it also causes the hitch head to follow. The motion is a pitching back and forth of the hitch head. On my hitch the pivot point for the hitch head is six inches below the top surface. The Trailair jaw with hitch pin is 8.5 inches forward of the pivot point for the lower jaw and 2.5 inches above hitch surface. When hitched together the two pivot points are separated by a vertical distance of 8.5 inches and a horizontal distance of 8.5 inches. The pivot point for the pin box is mostly free to move vertically up and down. This can be observed from inside the truck as the shock compresses and extends on the Trailair pin box. When the Trailair is moving the truck experiences chucking back and forth. The pivot point for the hitch head does not move very much vertically,so the vertical motion of the Trailair causes horizontal motion of the hitch due to the rigid contact between the hitch head and the Trailair lower jaw pivoting together.

This motion would not be as pronounced on a hitch with a pivot point close to the hitch head. It also would be less with a pin box that did not pivot. I intend to keep the hitch and get a MORryde rubber pin box. Several members of my camping club have that combination with good towing results.

I will update after the changeover.

vvusteve wrote:

Cummins12V98 wrote:
Get one of these and you WILL thank me!!!

got one thrown with fifth wheel purchase.here is your thank you

AWESOME! Welcome to the B&W HeavyWeight FanBoy Club.

x2 on the B&W companion puck mount or its slider version. I got the slider version and love it.

Had the rails already. Bought the B & W 18k Patriot. 1st tow last weekend from Cincy, OH to Syracuse, NY. AWESOME! Like it better than the Reese it replaced.

I paid a bit more but was happy to have my dealer install it. Anything wrong? Take it back to the dealer. Otherwise, be ready for the blame game. Installer will say it's the RV. Dealer will say it's the installer. One place does it all and you have nothing to worry about. Want to save a few bucks? I can't blame you.... my peace of mind is worth something.

Oh yeah, love my B/W slider BTW.

Cummins12V98 wrote:
Get one of these and you WILL thank me!!!

got one thrown with fifth wheel purchase.here is your thank you