Got down to the motor. The bell housing is broke. Mechanic said the crossbolt on the frame wasn't as tight as it should be. Our guess is that this allowed the frame to flex enough to break the bell housing. Found another bell housing for a decnt price. Found a set of good tracks, too. Starter, generator and voltage regulator have all been refubished. New battery cables have been made up. Next step is to get into the tranny and find out what we need for the reverse gears. Intend to replace all of the tranny bearings while we are in there. Going to cost me a few bucks, but all in all this bulldozer is in remarkably good shape considering it has seen nearly 50 years of use.