Cub Cadet 7234 Differential Lock Staying Engaged

[MajMac392]

I have a 7234 (gear drive, 23HP) model that I have had since new and just noticed the Differential Lock Pedal is staying engaged. This is the pedal by your right foot, just below the seat that you push down on to lock the rear wheels. It is supposed to be spring loaded up/disengaged but I noticed it was not popping back out. I took the adjustment rod apart where it attached to the differential and sprayed some penetrating oil into the lever going into the differential. That lever now moves freely and the Differential Lock is easily engaged by pushing down on it but it doesn't pop back out. Has anybody else run into this problem on a gear model Cub? I think it is the same type of foot pedal to temporarily lock the rear wheels that was used on other model Cubs made by Mitsubishi. The owners manual indicates an internal spring, I'm assuming in the differential is supposed to pop it back out of engagement but I can't find a spring on the parts diagrams. Any suggestions if someone else with an older Cub has had this problem?