There are 2 parts to an ignition "switch"....mechanical (key tumbler) and electrical (the switch) the electrical switch is what is suspect. You will have to remove the "cover" over the column (2-3 torx bit screws) and remove the 2 halfs. CAUTION CAUTION!!!!!! now you are in a place where a wrong move COULD set off the airbag....dont short any wires...at this point im "blind" with out going out and removing mine and typing at the same time .......but its not much diffrent than removing a power supply from a computer.

 

Yeah the ignition switch powers the trannys electrical. When the switch builds up resistance after so long it will go bad so the tranny goes in limp mode. Most of the time 2nd and 3rd gear will only work.