TC33D: Can't Engage Differential Lock

[barbque5]

I recently purchased a 2003 NH TC33D. The differential lock pedal cannot be pressed down because the rod from the transmission that it is linked to appears to be stuck. My guess is that it has never been used in its 9 years of existence. I have tried dousing the rod where it comes out of the transmission with penetrating oil, pressing with all my 210 lbs on the pedal, and tapping the pedal with a hammer (but not too hard for fear of bending the linkage), and no luck. Anyone know a technique or have a suggestion of what I could try? Is the rod supposed to be able to rotate? i.e. would it cause damage if I clamped onto it with a vise-grip and tried to rotate it? What about tapping the rod inward?

[Kernopelli]

I cant tell you first hand what directions to move the rod but being able to see the internal workings can sometimes be a big help. You can go to Messicks NH parts diagrams and look at the diff. parts diagram and possibly get a better understanding of how the rod, fork and lock mechanism moves.

[jinman]

BBQ5, when you step on that pedal, it moves a shaft attached to a shifter fork inside the differential case. The shifter fork moves a "clutch" with four fingers to mate with the differential gear case and lock both axles. If the differential lock is engaged while the tractor is moving, those fingers can be damaged or bent. All you will do by forcing the pedal or shaft is to do additional damage. If you can't see something binding on the shifter shaft externally on the linkage, there is certainly nothing inside that is going to be cured by slamming or hammering on the engagement lever or shaft. Differential lock works smoothly or it is broken/malfunctioning. What you are doing by forcing the shifter is the same as trying to force a shift lever on a standard gear transmission. You will only make the problem worse internally or break the external shaft in the process. You will have to go into the differential and fix it or just live without differential lock. I'm pretty sure the former owner must have engaged the differential lock while the tractor was moving or turning and messed up the lock clutch fingers.