hydrostatic transmission expert needed

Nhbalerman · Dec 9, 2017

I am new to the forum and have a question about a New Holland 912 speedrower that uses the same vickers hydrostatic transmission as some of the skidsteer loaders. I bought this machine and it has been setting for about 8 years and trying to get the hydrostatics to work, I changed the fluid and flushed out the system and changed filter it is getting fluid flow from the four lines no air and I cant get the tires to move,have it jacked up off the ground the wheels will freewheel turned the winching valve and can not get it to work,removed the linkage and operating it by hand,taken the cover off the 90 degree gearbox and the gears are turning but nothing from the output shaft from either motor can somebody help me? Thanks for letting me ask this on this forum,seems like a lot of good info here

Mike10 · Dec 9, 2017

First thing to check is the charge pressure. There is a check valve in the return from the cooler which directs 65psi oil to the center section of each group. You might also want to remove the relief valves to see if they are stuck open. If the machine was setting that long with the winching valves turned so the unit could be moved, then it is possible the the valves are stuck. They are on each side of the winching valve in the center block, at least on the cessna transmission. I think the Vickers are the same setup.

Nhbalerman · Dec 9, 2017

Mike10 said:
First thing to check is the charge pressure. There is a check valve in the return from the cooler which directs 65psi oil to the center section of each group. You might also want to remove the relief valves to see if they are stuck open. If the machine was setting that long with the winching valves turned so the unit could be moved, then it is possible the the valves are stuck. They are on each side of the winching valve in the center block, at least on the cessna transmission. I think the Vickers are the same setup.

Thanks Mike,I was going to check the charge pressure but didnt have the right fittings but will get them. I finally got one side working but the other side still want work maybe air or something but I keep cycling it and hoping,I checked the valves looked in the parts book to see where they are at but still just the one side started working

Nhbalerman · Dec 10, 2017

Mike10 said:
First thing to check is the charge pressure. There is a check valve in the return from the cooler which directs 65psi oil to the center section of each group. You might also want to remove the relief valves to see if they are stuck open. If the machine was setting that long with the winching valves turned so the unit could be moved, then it is possible the the valves are stuck. They are on each side of the winching valve in the center block, at least on the cessna transmission. I think the Vickers are the same setup.

Mike I checked pressure at sending unit and it was 90 idle or all speeds so I took the moter off the right side,just the motor and some of the pistons were broke so I guess there is my problem,looks like NH doesnt offer them anymore it is the vicker do you know where I might find these parts even used would be good. Thanks