73pete Posted May 17, 2017 Report Share Posted May 17, 2017 New to site . We are using an antique 1973 Peterbilt 359 with it's original Holland ffth wheel and are going to install a Trail-air pinbox. Does or has anybody used this setup ? Our trailer is a 2003 Newmar Mountain Aire 38.5 feet and weighs about 21,000 GVW. It has two 12K Dexter axles with dual wheels . Is the Trail-Air air pinbox a good choice? I pull regular semi trailers is the reason I haven't changed the fifth wheel. Link to comment Share on other sites More sharing options...
RandyA Posted May 17, 2017 Report Share Posted May 17, 2017 I am assuming that the TrailAir pin box you are referring to is one with a scissors jaw and air bag (I have one on my fiver). They work well if you do not have an air bag hitch but you will need to be sure to get the correct size air bag in the pin box for your pin weight. If your original Holland fifth wheel is like what we see on semi tractors that pull commercial trailers it will only rotate fore and aft, it will not rotate left and right like an RV fifth wheel hitch. I personally know of two folks that pulled their 5th wheel RV with a commercial hitch that ended up damaging the cross members and breaking welds in the trailer and requiring significant money and time to repair. Their trailers were not Newmars - it is possible that the Newmar is structurally strong enough to endure the twist on the front of the frame but personally I would not want to risk it. As far as the TrailAir (Lippert) being strong enough to take the stress of left/right rotation I think you need to ask yourself what part is going to be the weakest link and subject to failure - something is going to have to give. The TrailAir is an extended pin box and will be subjected to more twisting force than a straight drop pin box. All that said, some folks have been able to use the commercial fifth wheel without incurring any (known) damage to their trailer. My guess is they are towing mostly on decent Interstate roads and avoiding the rocking, rolling, uneven surfaces that have shoulder side dips and rises. I would love to see your '73 Pete some time. Do you have any pictures you could post a link to? Randy, Nancy and Oscar "The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks. ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired! Link to comment Share on other sites More sharing options...
JRP Posted May 19, 2017 Report Share Posted May 19, 2017 73pete, I used that same setup on my Volvo HDT & 39 ft tri-axle Teton combo with no ill effects over 6 yrs use. I was very careful to avoid or go slowly over any off camber type obstructions that exert lateral stress. I also only moved this combo 3 or 4 times a year, since I used my Motorhome as my primary RV and the Volvo & Teton were secondary, only used to setup an extended temp winter home. In my opinion the air pin box makes it better than a fixed pin box, but not as good as a fully flexible air hitch. I recently sold my Volvo Hdt & Teton, and a very thorough inspection showed no frame or weld defects. The Tetons were built with heavier frames than most others in their day. Jim Link to comment Share on other sites More sharing options...
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