Box The Frame Above Leaf Spring Mounting Points?

I am in the middle of the restoration of a 1974 CJ-5, currently working on the frame before I blast and paint it. I was doing research on the original paint code (527: Golden Tan Metallic) and found a beautifully restored 1974 CJ-5 Renegade listed on this site: 1974 Jeep CJ5 | Canyon State Classics .

The listing states that it was "out of the collection of a
35 year Jeep dealer and expert who just recently completed
a full frame off restoration on this gorgeous CJ-5. ...While the
body was off, the frame was boxed above each leaf spring mounting
point, to strengthen the Jeep substantially."

Would this be a good modification to do? I would box each frame section for a length of approximately 4" at the rear leaf spring mounting points using 1/8" steel plate, the same gauge as was used in the boxed sections of the front of the frame on either side the engine.

This Jeep is going to be mostly a restoration, with only small modifications (electronic distributor, 31" tires, twin stick for the t-case, things of that nature), not a hardcore off-road/trail rig. I would not want to prevent the frame from flexing as designed, potentially leading to fractures. But I would like to add some rigidity at key points if it would help.

Thoughts?

 

where in nebraska are you? sorry, not related to the question, but i'd like to meet some other ecj5ers.

i'd say it's a good idea for a lot of strength, especially if it's going to be treated rough, but if you're going to go easy on it, not necessarily required? i am most definitely not qualified to talk about this stuff with any certainty

 

I boxed my frame around the spring hangers after I discovered the frame flex cracked the C channels (I've since boxed the entire frame). It was an easy first fix for an offroad rig that was seeing a lot of use. Boxing around the hangers doesn't degrade the frames ability to flex or cause any other problems.
If you are dong a "resto", the frame isn't badly cracked, and the Jeep isn't gong to see anything but light usage, I think boxing would be more of an upgrade than a necessity and probably not worth the time.

 

I’ve done this in the past. I fish-mouthed the ends of the plates so that, in theory, vertical strength was retained, but torsionally it had some give. Welds were also done in separate chunks; if one weld cracked free, it wouldn’t continue through the entire length of the plate.

 

It would appear I am in the same part of Nebraska as you, I'm near Hastings.

 

This is exactly what I was thinking of doing, but I would probably form the brace as a "c" to fit inside the frame rail, similar to the way the front of the frame is boxed. Great idea to fish-mouth the ends to dissipate the stress.

How many miles do you have on your braced frame? Any issues or things you would have done differently?

 

Maybe one mile?
It’s @tomasinator ’s frame, and he’s only taken it for a test drive or two so far.

If I’d do it again, I’d probably go with smaller welds. Your goal should only be to prevent shackle mount twist, not prevent frame twist. I almost like Howard’s method better, because his would achieve that goal with more success.

 

Here's .1 of that one mile on the reinforced frame

 

Yeah his method looks solid as well. I suppose I could achieve a similar result with angle iron and a plasma cutter. It would probably help keep water from sitting inside the frame as well.

 

That's a nice looking CJ! What tire size are you running?

 

I believe those are 33"s. They came with the completely disassembled jeep. The tires are old, perhaps from the 70's or 80's. They are "Remington Wide Brutes".

 

I believe I'll use the same method as the factory used to reinforce the bump stops, one length of 1.5" angle iron welded in between the two rivets.

And I think it would also be a good idea to cut out and re-weld the welds the factory made between the riveted spring mounting brackets and the frame: it looks like the work was done by a blind man on his first day using a MIG welder.