This is the overdrive rail switch that is used on 2WD models with the Borg Warner overdrive. This switch bolts on the overdrive housing and is activated by a rail to allow the over drive to be engaged or not. The later overdrives usually don't have the rail switch because they were designed to not be used with it.
Note: Later overdrives used on the T90 usually dont have the rail switch. Check before ordering.
1 Required per Jeep.