OK, time for the physics lesson. Draw a line - mentally - from the bottom bolt holes on the left to the bottom bolt holes on the right. Now, mentally again, position a receiver in relation to those holes. You will notice that the receiver is a few inches below the line of the bottom bolt holes. When you pull on the hitch, the bottom bolt holes act as a fulcrum. The hitch system pulls on the bottom bolts and pushes on the top ones...ie a twisting motion on the cross member. If the cross member was strong enough, it could withstand this twisting pull. It isn't. In addition it is also not strong enough to keep the bolt heads from pulling through the metal.
Solutions:
1) an 18 wheeler - had to throw that in. Hope you don't mind.
2) Heavier cross member
3) Attach hitch to frame and cross member.
4) reinforce cross member.
1) Macks are good.
2) Lots of work. Still have to form a good attachment to the frame rails, and the twisting motion still has to be delt with.
3) There are two threaded (about 1/2") bolt holes on the bottom rear of the frame on each side. Assume these holes are on most Jeeps. The few that I have seen have them. If you attach a good heavy piece of steel to the bottom of the bumper and into those holes, the pull exerted on the receiver is directly against this new connection because it is lower than the bottom bolt holes in the cross member. It is a strong connection, cheap and easy to do.
4) The cross member can be reinforced in several ways.
a) bolt a heavier piece of steel to the inside or outside of the cross member itself.
b) weld it instead of bolting it.
c) sandwich the cross member between two pieces of flat steel.
d) heavy angle iron instead of flat steel
All thse solutions DO NOT include attaching the reinforcing steel to the frame. Reason I mention this is that once you put heavier steel behind, in front of or sandwiched around the cross member AND attach the reinforcement to the frame, what you have done in effect IS NOT reinforce the cross member. You have instead built a new cross member. Splitting hairs, maybe, but just trying to cover all the bases.
Personally, I have seen the steel strap connected to the two bolt holes do some amazing pulling with no twisting, no damage, no breakage. My first choice. Cheap & easy & strong. I think that most of the commercial bumpers sold for real pulling make this attachment. On my TJ with the TomKen the piece of metal is about an inch or so wide and two or three inches long with a half inch or so hole in each end. That's all it takes - well with the bolts, of course.
Doug '97 TJ
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