Another Tranny Issue

[georgestr]

I drive a 1998 Navigator, 5.4l, and recently have run into a seemingly serious tranny issue. When I accelerate from a stop, the engine seems to stick, or hang around 1400 RPM's before an odd sounding shift. Through the rest of the gears, it just seems to shift in different places. Has anyone ever had something like this happen before? Will this cost me an arm and a leg to fix?

Any help is appreciated.

George

Edit: I have about 135,000 miles on the truck, and tow a medium weight trailer from time to time in case it matters.