Sorry if none of this makes sense, I don't operate the backhoe, my dad does. He says he put 5 gallons of hydraulic oil in and the backhoe will not go forward or backward. Does anyone here know what is the problem?
Check power from the FNR switch and to the coils on the trans
If it's really a 420 - they were first made in 2000 - check the left side of the front dash for a red switch. If it's there it's the transmission lockout switch. Make sure it's off. If it's on, the FNR lever will be locked out.
Whoops, I meant 426... Should I still do the same thing?
I believe the dash mounted neutral switch was first used with the B series in 1992. I don't think it was used on the A or series 2 machines. Just don't remember. If you're not getting any movement out of the machine, I would first check the Trans disconnect switch on the loader lever to see if it is stuck or not making contact.