Washer would try to agitate during spin cycle.

Very old washing machine began to make a horrible noise and agitator would attempt to agitate during spin cycle. Eventually determined that the problem was in the transmission. The way the transmission works is that when the motor runs in one direction a metal fork pushes on a cam mechanism and lifts a spring loaded gear on the agitator shaft from the gears that make it move, putting it in neutral so that it can spin freely with the basket in the spin cycle. When the motor runs the other way the same fork pulls on the cam and drops the gear down so that it engages with the agitator mechanism. The problem was that the plastic cam pieces on the base of the shaft had worn down to the point where they where not fully lifting the gear clear and it was partially engaging with the drive mechanism. Repair was relatively straight forward except the YouTube video that I was using showed the parts on upside down. All the other transmission parts are labeled with TOP on one side but oddly the cam pieces are not marked. For reference the U shaped protrusion on the cam parts goes on the top of the assembly, not the bottom. All in all it took me about 12 hours to do this fix, but at least 10 of that was simply trying to figure out how the mechanism worked and tracking down the problem. Be sure to refill the transmission case and use some RTV sealant to seal the cover back on when you are done, just like you would for an oil pan on an engine.