Since it is at the top of the shift tower, it would be for back up lights. The 4104 used to have one by the transmission oil pump for low oil pressure.Does yours have this also? If it does, it would be mentioned in the operators manual.
There is another switch with a single wire mounted next to where the trans oil filter is mounted. According to the manual that one is for the low pressure light. Makes sense that the switch in question is for the backup lights then.
Thanks for the clarity on this.
On a related subject, since the picture shows it so clearly, anyone found a better rubber boot for the reverse solenoid? You can see what happened to mine - this one only lasted about 8 months. The one before that only about 4.