Skid Replacement and Frame Repair

by Zach Heisey for FSJ Magazine

A little old lady brought us her really nice 1990 Grand Wagoneer with the gas tank all but dragging on the ground. Turns out it wasn’t the tank, it was still held in by the straps. It was the skid plate and the rubber liner that goes around the tank that was hanging down. One look at what was left of the skid plate and the frame and we knew it was major repair time.

Safety Notes

Drain as much of the gas as possible out of the tank before attempting this job. Don't assume it won't be very heavey because it only has half a tank. Even empty, these tanks are bulky. Get a friend to help you take it out and install it.

Don't have the tank laying anywhere near the vehicle when welding, as the fumes could ignite. Also, drain the fuel lines on the vehicle.

Wear proper welding gear, i.e. mask, gloves, shirt as you will catch lots of sparks doing this job.

As you can see above, the entire lower portion of the C channel was rotted away. The fuel and brake lines behind the tank were also very rusty and brittle and the brake line actually broke when I was taking the clips off to move the lines out of the way. We’ll talk about the lines later.

It’s a good thing Jeeps don’t rely on the skid plate to keep the tank in place because the tank in this Wag would have parted company long ago. The straps were holding the tank in place, but because the skid plate had held dirt and moisture all these years, the frame by the tank, the straps and the skid plate were all rusted. Pictured [in figure 2], the only remaining portion of the skid plate was near the driveshaft and around the front and back. Nothing near the frame survived.

Tool Box

Basic Hand Tools
Tetanus Shot
Grinder / Sander / Wire brushes
Lincoln 255 480Volt Welder (Any welder that can do Ľ” in one pass will do.)
C-clamps
A vehicle lift or jack(s) and sturdy jack stands.
Vise, 2x4s, Drill and drill bits

We obtained a used skid plate and cleaned it up. Then it was time to get parts to repair the frame. Where did we turn? FSJ magazine of course, and more specifically, to Auto Rust Technicians (www.autorust.com). We compared several of the kits offered by other companies and they are tin foil compared to the three piece kit that Auto Rust offers. After a quick call to Auto Rust Technicians, the three beefy pieces arrived. We were very impressed with not only the thickness, but also the quality of the fit and placement of the holes in these pieces. These are not just hunks of plate with some holes cut out, these are well engineered, laser cut, precision welded repair parts made especially for our FSJs. The three pieces are, from top to bottom: the inner frame support, the outer frame support, and the rear frame support.

After removing the tank, draining the fuel lines, and moving all the lines and wires, the inner plate can be fitted. Although it is hard to tell from the picture, all the cut outs are exactly where they need to be for the contours and holes in the frame. At the bottom, where the parking brake cable goes through, you should remove the cable and feed it through the new plate. We chose to slot it and weld it solid. After getting the plate in place, mark around it so you know where to clean up for the welds.

Anyone who welds will tell you it’s a lot easier to weld when parts are clean and down to the bare metal. Some rust is OK but you’ve got to knock the major hunks off. Our red paint line has been brushed away and is just about ready to weld.

We recommend you clean up all the areas to weld for all three pieces before you fire up the welder. You also want to have the outer piece bolted into place and clamped before you weld in the inner piece to make sure everything stays in place and lines up properly. We welded the inner piece in place and the outer piece bolted on through what were once the stock holes. You’ll notice right in the middle of the large cut out is a nut. That is the spring eye bolt. Do yourself a big favor while you are in there with the welder. Weld the nut to the bracket because those welds always break when you are trying to change leaf springs.

The outer frame support has a cut out for the body mount and has three large holes for additional welds. After tacking the outer piece in place you can rosebud weld the holes to the frame. (“Rosebud” weld means you see the hole as another edge to weld to the frame and you go around in a circle until you fill the hole. When a welder does this, and it’s pretty, it looks like a rosebud.) Then with it tacked and secure, you can weld around all the edges and finish it. The rear support piece on the outside of the frame, behind the leaf spring is the toughest to install because of all the things in the way. You need to get it in behind the leaf spring and against the frame on the side and bottom and make sure it doesn’t stick out and rub the leaf spring. You also need to drive it forward with a hammer (just a little) until everything aligns properly. We clamped up from the bottom in order to hold the piece against the bottom of the frame so it could be tacked near the spring.

Then a second clamp was put on to pull the piece tight against the vertical part of the frame, and then tacked. After everything is tacked in place and properly aligned, double check to make sure the new piece won’t rub on the spring. Then weld it solid around the edges and put rose buds in the holes.

Now that the frame is taken care of, we need to look at the replacement skid plate and straps to make sure all the parts are there and will fit together. One part that wasn’t salvageable from the old or replacement skid plate was the triangular mount that goes back near the wheel by the leaf spring.

You don’t have to be a master fabricator to make a bracket like this. We found a piece of sheet steel laying around the shop and, using some cardboard, a pencil and a ruler, figured out the complete original shape of the piece. Once the cardboard cutout was done, we transferred the shape to the metal, including the bend lines and mounting holes.

Using the classic Hillbilly Brake (a vise and some 2x4s) we bent the metal along the lines and drilled out the holes.

The replacement straps held the tank nicely and the skid plate fit like brand new. The Auto Rust Technicians kit comes with new hardware for the frame. This includes a thin nut that goes between the frame piece and the skid plate. This deliberate gap allows water and dirt to drain out preventing future rust problems.

While you still have the tank out, this is an excellent time to replace several items. First is the brake line. We had no choice as the rear brake line came apart when it was removed. A single piece of straight brake line long enough to replace it with one piece was unavailable so we made the rear brake line from three pieces obtained from any well-stocked auto parts store. The first line you need is the one that adapts the large fitting coming out the combination valve down to the proper line size. When purchasing your lines, take your old ones along to make sure you get the right size and thread. Then get two pieces of 40” straight length, two double female adapters, and a hand tubing bender and bend away. If you’ve never bent brake lines before, get an extra piece of tubing. It’s not difficult, but it takes a couple of bends to get the hang of it.

Notice the second union in the line occurs just before the frame starts to bend. The first long length didn’t need much bending but the second did. And of course, the fitting into the rear rubber line down to the axle was so rusty it broke, so a new rubber line was also installed. Start soaking all the brake lines when you begin this job. Just keep the fluids away from the welder.

Amazingly enough, the fuel lines were in good shape, so only the short rubber pieces were changed. And lastly, there was no point in removing the gas tank without putting in a new sending unit. Yes, you guys with later Wags have it easy with the access hatch in the back under the carpet. Those of us with older Wags and Cheros don’t have that luxury.

While this repair was done on a 1990 Grand Wagoneer, the process is basically the same for all Wagoneers and Cherokees, 1962-1991. This job not only made the Wag safe to drive again, it now actually has a working fuel gauge for the first time in years.

Sources
Auto Rust Technicians
1-800-407-7024
www.autorust.com