Speedometer Drive
The speedometer drive has two seals that should be replaced. The outer O-ring is obvious, but there also is an internal seal, which often fails and is a common cause of transmission-oil leaks. To get to it, you must first remove the drive gear, which just slides out, then unscrew the seal retainer piece, the one that looks like a large hex nut. Inside, there is a steel washer that must be removed, even though it probably is rusted in place, and then the seal can be extracted with a puller or hooked wire. The smaller nut locks the right-angle gear into position. It can also be loosened, allowing the gear housing to be unscrewed, and the gears then can be cleaned and regreased.