Does your shifter wiggle left and right when it's engaged in a gear?
If so, this might help point you in a direction.
My shifter was getting increasingly loose. Once engaged, it felt fine. The gears were clearly meshing.
But it got to the point where I couldn't get it into first or second without slamming the shifter against the left gate and then sliding it up or down into gear. Totally sucked.
I took it to a Ford dealership, who determined after several days that the cable shift linkage had come loose. They said it's attached to the transmission by four bolts, and that one or more bolts had stripped and slipped out.
They re-tapped and re-bolted all four.
No parts needed replaced.
It felt great when I got it back. Tighter and more precise shifting than I'd ever felt.
That lasted two weeks.
Then it started loosening again.
To make a long story short, I ended up quite displeased with Ford and took the car to another mechanic. He wasn't able to determine what Ford had done, where the four bolts were that they said they replaced and whether the problem really was a loose linkage or whether it was something else.
Mechanic #2 told me to wait until it got so bad that I couldn't get into first or second again and then to bring it back so he could start digging.
I'm ready to take it back to him this week.
So, I don't have a definitive answer for you, but you may want to suggest to your mechanic that he look at the linkage.
