Sill Cover Replacement - 1977 FJ40 (1 Viewer)

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Jan 24, 2020
Threads
8
Messages
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Location
Portland, Oregon
So to start, I’m new to sheet metal work but have done small part fab before. Trying to tackle some of this on my own.

As far as I can tell, the sill cross member behind the round side of the quarter panel has little to no rust. After tearing off the sill cover, I found rust on the top of the cross member in a few areas, but the metal appears to be repairable.

So my question: can I patch/integrate sheet metal into the existing cross member, and then install the sill cover? Or do I need to do a full replacement of the cross member. Now, if you look inside the cross member, it’s rust free. I can even see the original color of the steel coating. And the steel behind the quarter panel is free of corrosion.

I’d be curious to know thoughts/advice on this.

This rig is not a restoration. I enjoy driving them on trails with light off-roading. I’m including the before and after removal of sill cover pics.

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More pics. Again, I removed the sill cover. This is the exposed cross member. I cut out the cancer already.

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The main sill is structural. I wouldn’t be patching it. Beside the tub hard top is putting a lot of downward force on the sides of the sill. It thebone continuous piece that support the ends. Not sure about the ambulance door model with the notch but my 73 FST the top and half way down the back are three layers. The main sill, the back floor then rear cover. On my 73 FST this is the worse rust.
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The sill is still intact. Because it will not have to support a hard top will just patch the quarter panel. May look at some extra support inside the sill because the spare tire is support on this side. Other side would not be a concern.
 
My '77 40 seems to have rusted first on the sill piece. I believe it was left in the rain and just sat like that for two decades. The PO did not drive this vehicle for about 25 years. For this reason, there's little to zero corrosion underneath the vehicle. There's also no corrosion on the curved parts of the sill support behind the rear quarter panels, just the top of the sill. Looking at other rigs that seems to have corroded from water/debris getting caught during driving, I can see how that area would corrode. However, mine is different.

Given these circumstances, would a patch in the areas where it rusted suffice? Again, there is zero corrosion where the cross member extends to the curved part of the quarter panel. I'm not trying to short-cut process. I honestly want to know opinions.
 
Here's another option you might consider--I had similar corrosion--Replaced the whole sill with a 2" steel tube-chamferred the tube to fit inside each side of the cut-out original sill, then welded in- done ~12 yrs ago - no issues since--sorry there are no progress pics I took--only before and after--

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nice! What year is yours?

Mine is a 77 and has the little step on the edge. I ended up reconstructing the bad parts of the cross bar then welding on the sill replacment.
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I'd go ahead. Just be sure to cut out all of the rust and get back to solid metal. If you treat and kill the rust it should be all right.

That said, if any rust is left, it'll come back eventually... but I'd do it.
 
Yep, I did. It turned out great.
Excellent... I overlooked the initial thread date.

I wish tubs here were 1/2 that nice... I see "rusted out" beat up tubs being scrapped that are way nicer than anything we get to start with. Back in '92 when I built a new floor and inner fenders, the original sheet metal folded up like newsprint when I threw it into a rear load garbage truck.
 
Excellent... I overlooked the initial thread date.

I wish tubs here were 1/2 that nice... I see "rusted out" beat up tubs being scrapped that are way nicer than anything we get to start with. Back in '92 when I built a new floor and inner fenders, the original sheet metal folded up like newsprint when I threw it into a rear load garbage truck.
My appetite for repairing rust has more to with my weekly pain threshold than the actual rust on the vehicle.
 
I would have cleaned and repainted that crossmember. The steel thickness used was in excess of the actual requirements structurally, IMO, so if it's just surface pitting, and the pits are at least a pit diameter from each other and less than 0.030-in deep, you're fine. Especially for the use you described.

Really good repair job. If you're ever in Charlotte, please come by and fix mine. ;)
 
nice! What year is yours?

Mine is a 77 and has the little step on the edge. I ended up reconstructing the bad parts of the cross bar then welding on the sill replacment. View attachment 3175781


If you look at the post above yours will see it had the catch for ambulance doors as well. Not sure how that was handled. The center section of the sill where the floor meets has the less stress than the corners that support the wheel wells and hard top. The continuous sill helps with leverage with the weight from corners. From what I've seen over the years a continuous weld underneath where the sill and floor meet would prevent moisture from getting in and being trapped. I have a few with rust free sills. What most have in common is they had auxiliary an fuel tank added which helped prevent moisture getting in the open seam underneath. Even heavy rectangular tubing will allow the lighter floor to rust if moisture is allowed to get in.
 
If you look at the post above yours will see it had the catch for ambulance doors as well. Not sure how that was handled. The center section of the sill where the floor meets has the less stress than the corners that support the wheel wells and hard top. The continuous sill helps with leverage with the weight from corners. From what I've seen over the years a continuous weld underneath where the sill and floor meet would prevent moisture from getting in and being trapped. I have a few with rust free sills. What most have in common is they had auxiliary a fuel tank added which helped prevent moisture getting in the open seam underneath. Even heavy rectangular tubing will allow the lighter floor to rust if moisture is allowed to get in.
Yes, the trick is to prevent moisture from getting there. I honestly wonder how possible that is though.

As a friend once said, the only thing that’s water proof is a box with a hole in it. In other words, give the moisture a way to pass through, get aired out. But idk I’m just trying to get this old thing back in the road.
 

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