 1998 windstar/no reverse
Hi
I recently purchased a 1998 windstar gl. It has lost reverse, mostly. After sitting for a couple of months, I moved it about 5 miles and tried reverse just to see what happened. It shifted to reverse and worked normally. Smooth acceleration and no shuddering or hesitation. After shifting it would not go back into reverse. I changed the transmission fluid and filter. Fluid and filter looked very good. The magnet in the pan had some grey sludge around it but not too much.
When I shift into reverse nothing at all happens. No change in the engine sound. The reverse lights do come on.
My questions are, what can I check before replacing the transmission? Could the transmission range sensor cause this? | 
