I have the same problem. I took the seat apart to find the problem, and the sheetmetal that the seat back is made of was cracking. The seat back would have broken in half if I were rear-ended. I bought some metal from lowes, cut it to size and bolted a peice on the inside and outside. Long storie short: The seat still squeaks but atleast it won't break.

1998 Contour SE V6 MTX-75 Mostly Stock 1986 Ranger V6 4X4, the only mod: weight reduction by rust.