Mr. Science explains why BRAT wheel wells always rust out

   How often have you seen this on a BRAT? Here is why it happens and how to fix it: Inside the wheel well is a piece of stamped metal functioning as the shock support that rises up from the bottom, runs along the back of the wheel well and then bends forward at two angles before rejoining the top of the wheel well. It is on the flat formed by the two angles that the shock mounts to. Behind this flat there is a open space. This is the guilty party. What happens is that water gets sprayed up into this space, including salty water in the winter, and it runs down the space between the shock tower and the wheel well. The trapped moisture causes the rust to form and then the fender wells go.

If your wheel wells are just fine and no rust is present between the two plates, like if you live in Az, Then the preventative step is fairly easy. Simply clean up the area around the gap and cut out two plates from sheet metal that cover the sides of the shock tower gap and weld them in place. Finish them and give it a good undercoating treatment. Now no water will accumulate there.

For the rest of us the damage is fairly easy to fix as well. Don't underestimate the rust, the entire length of the parallel panels is probably rusty. Mine had two minor rust spots on the fender well and as I cut and trimmed I found that the entire length was rusty. What I did was cut away the fender well till I had a 1/4 inch gap around the shock tower on the other side. There was no rust present on the metal after that other than the surface of the exposed shock tower. That was ground off and treated with a rust converter. You have two real options now. If the truck is a working truck you will want to weld new metal over the cut-out and then follow the preventative procedure above to prevent it from happening again. Or, if the bed is not used you may use fiberglass cloth and resin. Follow that up with sealing off the gap as above.

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