rear frame C-channel

[disassociative]

I too am in the process of replacing the rusted out stiffener plates in the rear c-channel of my FJ62. I made measurements and determined that the maximum allowable height of the new material is 3.625" and the width (short arms of the "C" shape) should be just under 2.00" (did mine at 1.9375") to be flush with the existing C-channel.

I requested 1/4" steel plate with two 90-degree bends. The sheet is 6.75" wide with bends at 1.75" and 5.00" with a radius of 1/4". I should have the pieces back from the shop at the end of this week and hope to install them this weekend. I will post pictures and explain my results next week.

 

[disassociative]

C-channel replacement

So...I finally finished installing the stiffener plates in the rear C-channel of my FJ62. What was s'posed to be a weekend job took a bit longer than expected because:

1) I got distracted trying to remove the baked-in shackle bolt from the mount
2) I wanted to use a mill to drill all the holes and didn't have access to it until Monday...but it was SO worth it
3) It turns out there is some planning involved in applying Rust Bullet, in that the requisite drying time does not easily fit into an after-work schedule.

Anyway, I followed Melloj123's example (see thread) for addressing the rust problem with the stiffener plates and MSGGrunt's instructions (see thread) for the rivet removal. This is not a terribly difficult project to do with the right tools (particularly an angle grinder, drill and air hammer) but it does take a long time.

The first picture shows the old plates removed and minus all loose rust next to the new ones I installed (too bad there isn't a prize for worst case of rust). And before anyone says it, I know I SHOULD just replace the frame. All the repairs I'm doing to this one are removable so I can install them in the new frame when/if I find one and have the time to do the swap.

The measurements for the replacement stiffener plates are noted in my previous post, and it worked well. After the two coats of Rust Bullet on each part, they fit together snugly. I also removed the rear crossmember/bumper mount to extend the stiffener plate all the way to the frame. I am installing a new one tonight with a mount for a custom bumper.

Good luck to all the other brave souls tackling this project, hope this info helps.

 

[MSGGrunt]

Great job. Keep us posted on your rear cross member build. I'm going to be replacing mine as well and would be interested in seeing what you design.

 

[MSGGrunt]

Is 1/4" overkill? Weight? Would 1/8" or 3/16" work just as well? My repaired FJ62 frame will be used for a FJ79 pickup build and any extra strength will be nice. I'm looking to retain the FJ79's 1 ton carrying capacity.

disassociative, what did the two pieces cost you?

 

[disassociative]

Yes, I think 1/4" is overkill, but the cost difference was only about $6 per side from 3/16". I have a tendency to be ultra conservative when replacing structural components on my vehicle. I got two 48" pieces of channel for $60. A normal repair would only require one of them, but since I wanted them to run all the way to the back I got them longer. I would have been fine with 36", but I liked the idea of having some left over.

I used 3/8" bolts for the most part, except the suspension connections and the new frame mount which are 7/16". I will take a picture of the rear frame tonight. All in all, the c-channels, hardware, and paint (just what was used) for this repair probably put the cost around $100-120. I spent about 20 hours on the whole thing.

 

[disassociative]

Update

Just finished installing the new rear crossmember I made this week, pretty happy with the results. As is typical, it is overkill, but now I won't be worried the rust epidemic that laid waste to the rear end of the vehicle is likely to kill me or a loved one as I drive down the road or climb up a trail.

I measured the distance from center line to center line of the leaf springs at almost exactly 40.5". With the 1/4" stiffener plates installed and the width of the 1/2" brackets I intended to use, I cut a piece of 3"x2"x0.188" tubing at 39.5". I had originally planned to put an angle in it like the original, but I couldn't see a need for it and wanted my rear bumper as close to the tailgate and as far from the ground as possible without exposing the frame.

The images show the view from underneath of my connections and the new look of my rear end. Everything lined up quite well, and I only ended up being off by 3/16" on the width. I will insert a shim when I install the new suspension in a few weeks.

Cost of materials: $35
Time: 8 hrs

 

[MichiganFJ60]

Since there are already several posts in this thread compiling info about the channel, I've copied the relevant information from my build thread here. I'm also hoping this context might generate some more hits and replies to my question below. Hopefully I'm not violating protocol or anything.

I've been making slow progress, focusing mainly on painting the frame, axles and other bits. I got the final coat of paint on and turned my attention to replacing the rear c-channel.

A local shop bent up two pieces of 3/16" steel to tuck inside the frame rails. Before I clamp them in and drill holes for fasteners, I'm wondering if I should be at all concerned about the possibility of a hard line on the frame due to forward edge of the inner channel? I was planning on having the pieces sit as they're pictured here because angling them forward like the original pieces, and the little weld at the forward edge, didn't seem to add any real reinforcement. Am I missing something or making a mistake by locating them where I have them?

Thanks!

 

[disassociative]

As I recall, there was a weld on the original C-channel reinforcement. Perhaps it was done for this reason.

I did not put any welds on the C-channel I installed, in part because I extended the channel all the way to the rear of the frame. As a result, there were about 15 bolts on all sides of the "C" that I figured were sufficient to replicate the original structure.

 

[MichiganFJ60]

As I recall, there was a weld on the original C-channel reinforcement. Perhaps it was done for this reason.

I did not put any welds on the C-channel I installed, in part because I extended the channel all the way to the rear of the frame. As a result, there were about 15 bolts on all sides of the "C" that I figured were sufficient to replicate the original structure.

Yeah, this picture shows the weld at the forward end of the inner channel. It also reveals how ineffective it was as a reinforcement in that area - you can see how the upper and lower flanges are pulled/pushed away from the frame.

By contrast, here's the way the new piece will likely end up. You can see the remnants of the original weld:

Unless I hear otherwise, I'm going to assume that it's fine to drill and bolt this channel the way it sits.

Thanks.