1971 4320 lost hydraulics

[farmerjack]

once in a great while my steering would feel as though the steering wheel was locked for a second. going down the road last week. all of the sudden it locked and then lost hydraulics as 3 pt and brakes
didn't work either. as I was trying to get home I would be able to turn the steering wheel 120 degrees (like backlash) before I could command the front axle to redirect. parked it in my shop and 3 days
later I started it and the steering seemed locked a second and then was turning the front axle fine, but the 3pt chatters when being raised which it didn't do previously.

what are some ideas as to what might be causing it. I was thinking main pump or transmission pump relief valve. I don't have a stroke control screw in the main pump.

thanks,

 

[JIM MN]

Synchro transmission;; Trouble-shooting: Did you pull the hydraulic oil filter?? Tear it apart, is it plugged? Drain the hydraulic oil, pull the pickup screen; does it have trash covering it?? If all good; do the transmission oil pump quick test; is the pump pumping oil??

 

[Tx Jim]

(quoted from post at 19:34:10 06/08/22) Synchro transmission;;, pull the pickup screen; does it have trash covering it?? If all good; do the transmission oil pump quick test; is the pump pumping oil??

'71 4320 only had Syncro trans no Powershift option.

I suggest to check frt hyd pump drive coupler to be sure pump shaft is turning when engine CS turns. Also check hyd system pressure at rear hyd breakaway which should be 2250 psi.

 

[WTW]

The hydraulic pump pressure was momentarily lost when the pump stroke control valve either stuck open or got a very small piece of debris caught in it. Fairly common on older tractors to do this. Best fix is to remove and replace the stroke control valve and adjust pump standby pressure. This valve is a two piece assembly and has an O-ring and back-up ring installed on its outer diameter and another O-ring in housing. It is housed in the pump valve housing cover plate. It can be changed in the tractor without removing pump or cover from pump, as I have done many but is something you will not want a novice to do. A trained hand can do it all in less than 30 minutes. DW

 

[farmerjack]

Thanks Dave. Your brother Marv has been offering ideas too.

Jack