Deere 843J diff lock

[Nemologger]

The diff lock on my 843 Feller buncher wont engage, the light comes on and I can hear a change in the sound but it is not engaging. Anyone know what I might need to be looking at?

[kiko]

The diff lock system on these bunchers is fangled.  The diff lock system is a separate hydraulic system. The rear axle is the sump for the Diff lock pump. The diff pump is turned by an electric motor.  The suction hose must pivot with the rear axle and is prone to damage.  Also if there is a leak any where in the axle hydraulic system the rear axle could simply be out oil. Checking the fluid level in the rear axle would be the first thing to check.

[Skeans1]

May not hurt to jack it up and see if a shaft is busted as well.