Boxing Frame and Tranny Crossmember

I'd rather strap the frame top and bottom then box it
still get some frame flex that way
some flatties had factory strapping

 

Dan, mine is boxed the whole way. The shop that did it sorta stitch welded it ( 2-3" of weld then no weld for 3-4", and so on). I used a hole saw and drilled holes at the spots where I needed to access bolts like the ones for the crossmember. In retrospect, I think I may have welded nuts inside the frame at those spots prior to boxing it. When the 420 goes in I'll be making a new crossmember which I think I will have to bolt all the way through the frame. It will be made of angle and tubing I think.

 

The stitch welding is supposed to allow the frame to move a little. The suspension does the moving more than anything which, in my opinion is the way it should be on a short wheelbase vehicle like JEEPs. Pickup trucks need that frame flex. Just my .02. Sorry for the repost, again not allowed to edit for some reason.:?

 

:iagree:
As soon as I get the drivetrain out of my JEEP, I'm boxing the frame all the way. If you only box part, you end up with cracks where the boxing stops. I'm also going to plate the more crack prone areas, on the outside of the frame.

 

(Just my opinion ) the frame on your jeep needs to flex to make the suspension work right . i may be wrong but if you box in your frame you will make it stiff and you will be taking away from your suspension, making your springs do all the work,your fame needs to flex . but that is just my opinion

 

I boxed my frame front to back with 3/16. I cut the factory front "box" out and redid that too. I made a continuous weld, no cooling off periods, no attempt to control warping and it bowed out about 3" in the middle per side. My tranny crossmember is just a straight tube, flush with the bottom of the frame rails, welded in place. The worst part of the frame was just behind the front springs. Also cracked under my grill, around my front crossmember, and bent the bottom flange up at the spring hangers.

However this is for a rockcrawler with 38's, so going all the way was definately worth it for me.

I'm not a fan of frame flex. Frame flex=cracks (eventually). Frame flex also = poor handling and "feel"

 

I like to use these caged nuts, similar to the ones used by the factory to hold the front fenders to the grille shell. They give you a little wiggle room for locating the bolts. You can either spot or plug weld the tabs to the frame. They're available from McMaster-Carr.

tommy b

 

Box all the way! It won't take all the flex out of the frame. Steel flexes. As stated above, if you stop the boxing at some point, that's where it will crack. Excessive flex of the frame is hard on the body as well. I'm going to mount my cross-member (2" x 2" rect. tubing) to the boxing via bolts rather than the stock mounting on the bottom of the framerails. I think it will stabilize the center of the frame better.

 

I'm only at the "mental design" stage. My plan is to weld an additional plate on the boxing where the crossmember will attach, maybe 3/8" or 1/2". The cross member will have a plate welded on each end with four bolt holes in each one. Once that is fit I'll mark the holes on the boxing and drill and tap them for the bolts. But. like I said, this is a "design in my mind" concept at this stage and definitely subject to change. I like the design as you go plan. With forethought! Lots of forethought.!