thanks for the answers guys! I had a look and this is what I found. No split pin, but there was the remains of a cotter pin that had obviously failed. I have had this 155D for about 3 years now and I guess the previous owner replaced the split pin with a cotter pin. Unfortunately the two slots on either side of where the pin rides up and down in are now worn somewhat. I think the cotter pin head (eye) was catching in the one side.
Once apart I noticed other wear. The (not sure what I should call it) plate that the shifter goes through, that allows it to slide left to right is worn. Also the spring under the shifter ball, was deformed and caught up below that plate. I tried to reform in into the cone shape, but I can't see what stops it from sliding through the plate (which is what happened and allowed it to get wrecked. Did there used to be a washer or something below the spring or is it supposed to sit on that plate. Perhaps if the slot in the plate was not so worn, the spring could not get through. Also, I can see wear on the parts that the shifter ball moves to shift the gears. I don't know what these are called but they don't look easily replaceable.
Next question.....are there parts available somewhere? I would like to replace the plate that holds the shifter on top of the transmission, the one with the 2 worn slots that the split pin should ride in. Also the spring and the shifting plate below. Those I could replace myself.....and might get by for awhile. It would be nice to have the other inner parts that are worn replaced but I imagine that would have to be done professionally. I don't know any tractor mechanics anywhere in the town where I live....not really a farming type community.
