It's nicknamed the Ford Exploder for a good reason mate...tell him to sell it before it costs him even more.
And I do know what I'm talking about. We have one, biggest heap of shit I've ever had the misfortune to lay eyes on. Every gearbox shop I talk to reckons they chew through boxes like crazy, particularly the manuals. Ours is a 97 model auto and had 2 boxes replaced before we got it. It's not hit 250 000 km yet and is coming up due for another!
And that's before I start on the electrical issues, cost of parts, etc.
AFAIK these manuals don't use an external shifter linkage setup. I suggest the problem is most likely something to do with the shift forks inside the box, or the shifter itself.
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Proud TQE Operator and President of SEFAG - the Society for the Elimination of Ford Automatic Gearboxes

Pacemaker headers + 2.5" exhaust
EF Fairmont interior
MP3 player
Lowered King springs
5 speed manual
EF motor
Newest mod: EF Ghia wiring loom and dash