I just picked up a trailer for the boat I've been building, and after bringing it home, crawled under the truck to look at my smittybuilt bumper/hitch and where it mounts to the frame. I'd towed a heavy trailer all the way to AK from CA, and the bumper/hitch had angled down somewhat during the trip.

Anyhow, I see how the frame is a C section for about the last foot, and was thinking of boxing it in all the way back so it will be stiffer where the bumper/hitch connect. Anyone done this, and anything to look out for? I'm thinking 1/8" plate ought to be about right, and figure I'll cut out some access windows to access the rear bed mount bolts.

I'm also interested to see if anyone else has done this.

I was thinking of going with 2x3" box tubing finishing out the open ends and also creating another crossmember at the end of the frame.

I was simply thinking of enclosing the open section all the way back to the rear crossmember.

For the next or two I'll be using the truck to tow my boat ~3000# w/ trailer, and I figure I should beef stuff up back there a touch.

Eventually I'll get a 3/4 ton diesel for towing, but gotta make due for now.

I boxed mine, using rectangular tubing inside the C channel. Pretty much *had* to; I moved the shackle hangers back for longer rear springs. The C channel was not strong enough.

My spare tire still wiggles on the rear bumper even with this. The rear frame is very flexy. If I had it to do over (and we always seem to do over) I would extend rectangular tubing up into the frame as far as possible, then extend it out the rear for a bumper mount. 'Twould be much stronger.

The brackets for my rear bumper eff...no play in my rear-mounted tire carrier:





The brackets push forward to contact the internal bracing inside the frame and into the boxed section. They are a very snug fit inside the frame and even w/o the side bolts, you can jack the rear end of the truck off the ground with the brackets sitting inside the frame rails. There is still about 1/2" of upward flex in the frame with the rear of the vehicle supported by the bumper.

I used to run a Smitty-clone tube bumper in back and every time I used it with the HiLift, I had to push it back down level since it's brackets were a very loose fit inside the frame.

Those wrap-around side braces wouldn't hurt, either!

As is so often the case, I thunk of somethin', Roger has already done it, and cleaner. <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> <img src="/forums/images/graemlins/shiner.gif" alt="" />
<img src="/forums/images/graemlins/kewl.gif" alt="" />

Instead of taking the time to box it in, just run two diagonal braces from the reciever up to the bottom or sides of the frame. I weld pretty much everything on, but there's no reason you couldn't bolt it if you wanted to.

I'm missing several inches of rear frame (12" bed bob) and the bumper is a bit, er, dfferent than a stocker, but this design works very well. Yanked with it and been winched until I was pretty much hanging from that rear bumper tow point, and it's worked great so far.

Here's a pic from 2003, 3 rollovers and a lot of dents and cage work have happened, but it shows the rear bumper I've done. If you don't still have a spare tire down there, this is probably the strongest way to go:

A coupple of things come to mind, that you may have thought of already:

1. make sure whatever you build, it doesn't trap any water

2. make sure that, by strenghtening that particular section of the frame, (whatever you end up doing..), that you aren't just moving your weak point further under the truck. In otherwords, if you did hit this bumper hard (or pull really heavy), you would WANT the damage to your vehicle to take place out at the tip of the bumper.. where you can fix it. -just like it did the first time! :-)