I recently acquired a very clean 85 turbo wagon from a friend. The car has 98,000 miles and runs great but will not upshift into 3rd gear. (out of nowhere it just stopped doing it one day according to him) Reverse and the upshift between first and second are fine. Can you recommend anything I can do to help diagnose the problem? I have a spare tranny but I'd like to look into this more before going that route. Thank You.