Swapping a YJ Frame Into a YJ

If only my Jeep could talk, it would probably have a lot of stories to tell. Judging by the condition of its frame up 'til mere weeks ago, many of those stories would probably involve road salt. My YJ's original frame had the brown cancer pretty bad, and this summer it finally came time to replace the thing. This was preventative maintenance on a colossal scale - the frame hadn't failed (yet), but it was just a matter of time. Better to do this thing when I could prepare for it, rather than have to scramble to get it done after limping home with a trail patch welded in, right?

Besides, it was a great opportunity to get a few other things done; this kind of access to the Jeep's innards doesn't come along too often.

Swapping a frame is a project requiring lots of brawn and not much by way of brains, so in that light this writeup will be heavy on the photos and light on the verbiage. Here goes…

Here's the first frame I picked out at the local wrecking yard. Only cost me $250 CDN, since they've got a while stack of 'em:

Guess I should've had them pull it out of the pile before giving it the thumbs-up, though. Here's what I discovered on closer inspection:

In the photo on the right, that steel bar should be parallel to the square. Looks like frame #1 was an accident victim - the front half of the passenger-side frame rail was pushed in several inches! Very hard to see, eyeballing it, but plain as day once I broke out the straightedge and square. So a few days later, in came frame #2. This one was nice and straight. It was a '92, set up for the 4-cyl engine. That didn't matter much though, since I cut the factory motor and shock mounts off the frame after cleaning it up. Then I cut a bunch of 3/4" holes in the frame rails and welded 1/2"-ID DOM steel sleeves into them, to support the shock towers and the new motor mounts I'd be designing. You can see the two sleeves per side for the shock towers, and the four others for the motor mount brackets. I decided to bolt the brackets on for extra flexibility in designing the motor mounts, and to minimize the amount of welding on the frame:

After doing this welding, and removing the odd bits of rust, it was ready for paint. Painting the insides of the frame rails was a neat trick! You can see the duct tape on the holes in the frame rails in the last set of pictures. After taping up all the holes, I poured in most of a can of slightly thinned Hammerite metal paint. Then I lifted each end of the frame in the air, one at a time. Roll the frame 90 degrees and repeat, etc etc until the paint had run over all the inside surfaces. Finally, out came the excess:

This wasn't much fun to do, but the results were worth it. Hopefully I won't have to worry about this frame rotting from the inside out, like the old one did!

The outside of the frame got coated with Herculiner, a popular brand of truck bed liner. This stuff goes on really thick, sort of like painting with jet black oatmeal. It consists of a paint base with lots of little polyurethane particles. The end finish is a heavily textured surface that feels pretty tough. Again, I'm hoping for a good long life out of this stuff:

In the second photo there you can see the grey Hammerite inside the frame rail.  Amazing how good a coat of paint makes things look!

Next came the actual swap. First the teardown:


Here's a few detailed photos I took of the engine, powertrain, and other parts, just for kicks:

One of the things it made sense to put together while everything was apart was a new crossmember for mounting an anti-wrap bar to. Here's what it looks like:

The other thing I spent some time doing was redesigning my 5.0L motor mounts. When I did the engine swap two years ago, my first attempt at motor mounts was pretty half-assed. Not having a welder makes that kind of thing a real challenge. Here's what the new mounts look like, during and after assembly:

For comparison's sake, here's a shot of one of the old mounts:

The new mount brackets were surprisingly simple to make. After getting the engine where I wanted it, I just bolted the end plates in place on the frame and block, then measured/calculated the lengths of each corner of the connecting piece, and then welded 'em together. They're made out of 0.125"-wall steel plate and square tubing, with a little extra bracing on each one. They're swept back slightly to provide good access to the oil filter and the nuts on the bolts that go through the frame. The mounts themselves are the factory Mustang ones that came with the engine when I bought it. Easy to deal with and cheap to replace if I ever need to.

Meanwhile, the remaining Herculiner found its way onto the gas tank skidplate, the factory underbelly skidplate, and the underside of the tub. Here's some before and after shots of the tub:


Finally, the Jeep started to come back together:

Along with the stuff pictured here, I had a 3-row core put into the factory YJ radiator, installed a set of polyurethane body mounts, and put a Mustang vehicle speed sensor (VSS) in the EB D20 transfer case. Small things individually, but together they've added up to make the Jeep a lot more reliable.

Wondering why all this was really necessary? Here's five thousand words explaining why I think it was:



I'd like to thank Thomas Sternberg and Larry Soo for coming by and lending a hand during this 10-day ordeal. They both managed to show up at times when I don’t think I'd have managed without their assistance... funny how that happens.

Questions?  Email me!

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