My transmission has developed an odd downshift characteristic. While driving down the highway, and with no warning, the tranny will downshift from 4th to 3rd. It will not shift back on its own. If I come to a stop and accelerate back up to speed it will go back ito 4th but it's just a matter of time before it downshifts again. Sometimes when it has downshifted, I can put in in neutral and then back into gear and it will drop into 4th.

The first time this happened, I checked the fluid level. Itwas a bit low so I brought it up to full. The problem went away and I thought all was OK. Well, the downshift problem came back and the fluid level is correct.

Has anyone seen this before. And, should I cancel my vacation and use the money for a new transmission? Thanks