40series Crossmember Tow Package

[BU5H P1G]

Morning All,

I have removed the PO's poxy attempt at fabricating a tow package for the 40, and have installed a pintle hook / 50mm tow ball combo, which bolts directly to the rear cross member, through the four pre drilled holes.

I will only tow a very light ex-mil trailer (450kg or 1000lb max) - hence the military pintle hook - however does the rear cross member require stiffening to take the push/pull effect? I'm worried the little trailer will fatigue the steel and possible deform the member? Does a backing plate with braces back to the longitudinal frame need to be installed? Does anyone have some photos of a factory package? TIA

 

[watrob]

I built this, locked into the sub frame.

 

[lostmarbles]

Not factory... But this is how I obtained strength to my satisfaction on my BJ40:

And this is a thick plate that sits in front of the crossmember with four high-tensile bolts passing through it and one that threads into a hole I tapped right into that square section that I use for a bow-shackle when snatching:

 

[BU5H P1G]

Yes!

That is exactly what i was thinking!. i like that detail and finish watrob!

I will prob follow your lead Tom, as that is the path i have started down

thank you for your quick responses

 

[Fast Eddy]

I love the overkill, but I have towed a dead bronco II (3400 lbs) up a rocky 4x4 trail about a mile with a strap off of a receiver bolted to the rear cross member. I was worried when I did it, but it proved to not be a problem.

 

[BU5H P1G]

yes i agree that the cross member is (would have been) designed for a certain load, however my feeling is that my BJ40 has had a hard previous life.

The pressed metal member will be reinforced with a backing/compensating plate (approx 10mm thick) to prevent fatigue tear through the bolt holes in the member;
that plate will then be tied back to the chassis frame with two square or circular hollow sections (depends on material availability - high yield and decent wall thickness will govern). Ties will be welded to backing plate and bolted through two more plates on the chassis rail;
the complete unit should act in a tension/compression capacity in order to transfer the mid span load (exerted from trailer) received at the hitch to an acute linear load along the frame.
This should hopefully assist with relocating larger snatch/winch recovery loads further up the chassis and more toward the above rear axle stiffening circular hollow section.

wish me luck

 

[shelfboy1]

my 70 fj40 towed 12 6x6 army trucks to my house over its 35 year life span not to mention the tri axle trailer i towed with no problems .dumb maybey but these are tough little trucks and will take huge amounts of abuse

 

[Downey]

I have seen products on the market that were mal-designed merely due to their over-designing, adding too much unnecessary weight to the vehicle. Nothing you add to the frame needs to be stronger than the frame (rendering the frame the weak link). With that said, everyone needs to reach their own comfort level with their creations, and you've certainly done that..

 

[BU5H P1G]

You have made a good point Downey - no use making the main frame the weak link.

I'll ensure my work is only adding to the reliability (read: peace of mind) and not creating another issue - ie: reduced flex

thank you for the comments