1978 jd 300b backhoe worked great, then... Got stuck in mud, got it out .....now: tractor was fine with hydraulics for ten minutes after mud... Everything was fine... Wouldn't move back or forward and then no hydraulics for backhoe and bucket ... Changed both filters, cleaned tranny screen and it made no difference. I am trying to figure out where control valve is in front hydraulic pump. could it be bad? Any help is appreciated ! Thanks....
So you got it out, and then everything worked for ten minutes, and then the tranny stopped working, and how long after the tranny stopped working did the hydraulics stop? I'd guess the hydraulic pump doesn't have anything to do with it. The transmission MAY supply the charge pressure and that's your problem. Guessing, I'll try to look it up and see just how that one works. Did it do anything else unusual when it stopped driving?
Tractor Hey.. Hydraulics kept working for no more than 30'minutes total after losing tranny.. Tranny had loud hammering noise when started to not work...I think it's a closed system and the tranny pump provides pressure to front pump? I only know so much about it.. Thanks for your help, I miss this machine tremendously...
Yes, I believe the hydraulic pump gets it's oil under pressure from the transmission/reverser pump. So theoretically the hydraulics could work after the reverser has crapped out, or the reverser could grenade and the pump still provide oil for 30 minutes until it gets killed off too? It looks like there's a standard dry clutch in front of the reverser and oil pump, that could have let loose, or there might be another "isolator" in that line that could let loose. I don't know if there's any other way to diagnose this, but if you wait around somebody might tell you exactly what you need to know before you go splitting it. Apparently those reversers aren't terrible to rebuild if it comes to that. Was the noise definitely toward the engine? not the rear end?
Jd Noise was right below seat probably two feet forward , more on left side, and was hammering ..what is an isolator and how to check them?
The isolator looked like a coupling between the clutch and transmission, probably rubber if they call it an isolator, and probably not in as good of shape as it was 35 years ago. I'd be looking for any place that would give me a view of the "bellhousing" area, maybe take the starter off and see if you can get a mirror, or inspection camera in there to see if anything is obviously broken.