DIY fifth wheel hitch height modiification

Am pretty sure while going from 2009 BH 3055 RL to 2015 BH 3875FB that my hitch height is going to be a bit low. I measured current rig at level and also the new rig. There's approx. 2.75" difference. Might be partly due to 16" wheels on current and 17.5" on new but not sure on that. At any rate here's what I did:



3x3x25" steel tube in .25" wall thickness




Bolts went from grade 5 to grade 8 and went from 5/8-11x 2" to 5/8-11x4.5"



Once I'm sure this is what I need (picking up new trailer within the week) I will add welds in (8) places between the new risers and the original rails. Paint will also be applied.

All engineering experts are welcome to comment! Thx.

Not an engineer but it does look like something I'd come up with. But no comfort there!

and I know you have just spent money on the new rig but did you investigate what a new adjustable hitch would cost? You are taking on some liability here with your modification.

if you proceed, I would keep a close watch on the welds. It would seem any weakness would show up there as a crack first.

Don't know your hitch so curious what that line is running into the cab side is?

Garypowell said:

Don't know your hitch so curious what that line is running into the cab side is?

Click to expand...

Thanks for the reply Gary. A new hitch may be in the mix. The line is for air to the bladder. There is an onboard compressor mounted under the bed with a control in the cab for adding/releasing air pressure on the hitch.

Am curious to what others here may say regarding the 5/8" bolts. I personally would keep shopping for a bolt that has more shoulder and less thread if there is any available...this would allow the shoulder to go clear thru the bottom of your square riser. It just looks like those bolts are sacrificing a lot of shear strength with that much thread above a shear point.

Can't you lower the pin box?