Why do so many beds crack here?

[RenoHuskerDu]

We welded both sides up last night. Pulsed GMAW. Not pretty but we'll Ospho it and run that way.

This was pretty much a show quality bed, until our eldest daughter the advanced math major decided that it could occupy the same physical space as a sturdy cattle guard gate. Wailing and gnashing of teeth, big mallets and wood blocks, a bottle jack...still pretty wrinkled. But that's not what busted the upper forward bed corners. It just made one side worse.

Now it's just a functional bed, as we keep one eye peeled for another galvanized donor truck with a bed of this same color scheme (tan over brown).

[ArdWrknTrk]

Mine never tore across the stake pockets but it has torn straight across the front corners.... twice.

I MIG'd it up when I painted the truck in '15, and added a brace of box tubing under the front lip because it had bowed and was rubbing the back of the cab when crossed up.

I just think that's what happens when you constantly twist a four sided box.
The frame obviously isn't that stiff, and there is some bracing at the tailgate to help keep it from spreading.

[RenoHuskerDu]

I suspect that toolboxes are a contributing factor too. We're putting a headache rack on this bed next, and extending its "feet" back the length of the bed.

One of my sons, still a teen, did that welding btw. Had I done it, I doubt it would look better.

[ArdWrknTrk]

Well, you're teaching your kids skills that will serve them a lifetime.  

When I first built my lumber rack I just had tabs front and back of the stake pockets.
20' 2X12 rafters soon put an end to that nonsense, and I welded a continuous length of 1 1/4 angle lipped down into the bed. (think bedframe )
I also welded some washers between the three uprights on each side to that angle.
Providing a gusset and a tie down point for ratchet straps.

[Gary Lewis]

This discussion reminded me of this TSB: Documentation/TSBs/Body, Windnoise, Water Leaks, Trim/87-01-18 Tool Box Mount.  And in it Ford says:

Bolting the angle section through the inboard surface of the pick-up box top side rail and "shimming" the front and rear ends of the rail protector as shown in Figures 20 and 21 are mandatory. If the angle section rail protector or any rigid flat member is bolted along the length of the top surface of the pick-up box rails, serious permanent deformation and fatigue cracking will probably occur. This will result from the rigid flat member trying to "flatten" the side view "crown" and the "racetrack" offset in the 1980-87 pick-up box top rails. Figure 19 illustrates this side view "crown" and "racetrack" offset unique to the top rail surface of the 1980-87 F-Series pick-up boxes.

[RenoHuskerDu]

>I welded a continuous length of 1 1/4 angle lipped down into the bed. (think bedframe )
I also welded some washers between the three uprights on each side to that angle.
Providing a gusset and a tie down point for ratchet straps.

Got any pics of that mod?  The headache rack I have in mind for this truck only has about 3' "legs" towards the back, so far.  Needs modification in any case.

[ArdWrknTrk]

This gives you an idea how inadequate the tabs were and how attaching the downward lip not only stabilized the rack by tying the uprights together, but offered the full length of the bedrails to support it.