Similar story happened to me during the holidays. Stopped car, put it in park, got out, and then the car started rolling backwards towards the ditch. Luckily my girlfriend was still in the car and turned the steering to send the car in the street instead. Turns out that my auto stick linkage was loose due to losing one of the plastic grommets inside the loops at each end. Easy fix.

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Denis

1979 300TD 189,000 Miles, now running WVO with a home-made 2 tank conversion
1974 230 Gasser 189,000 Miles, For Sale
1961 VW Microbus 162,000 Miles
1961 Ford Fairlane 500, 53,900 original miles
1951 Oliver Super 55 Tractor
2002 Chocolate Lab