After driving my car at highway speeds for a while, then when coming to a stop, just before I stop, the transmission downshifts into 1st with a hard clunk. It continues to do this even when driving in city traffic. When it started doing this it was just every once in a while. Now it happens a lot, but it doesn't seem to start until after driving it on the highway. Any ideas what is causing this? FYI, before I bought this car last winter, it had been sitting for at least 15 years without being started.
1962 Galaxie 500XL
1962 Galaxie 4 Door (Eventually to be a Police car)