JD 400 Backhoe filling transmission by draining the implements.

[veewee]

This unit is causing me much grief! I fill the header tank above the pump, and everything works for a short spell, but then it pumps this oil into the transmission, thus overfilling it. I have replaced the hydraulic filter and removed the valve and spring that seems to isolate the oil flow through the large diameter hose at the bottom of the filter body, and that seems to be the only connection to the transmission reservoir. This valve consists of a ball-end and spring and almost sealed off the oil flow as I was replacing the filter, as there was only a slow dribble. The other plug in the filter body is just that, without any valve inside. The JD Parts drawing shows a valve setup and I ordered these parts but there is noway there is enough room to fit them, so I assume that they refer to a different setup to my unit. ( $76 wasted!) Can someone out there please give me your suggestions.

 

[Tractorboy88]

Leaking charge pump in transmission?

 

[jb1390]

Are you referring to the small tank located above the high pressure pump, near the radiator?

You are not supposed to fill that with oil......it is filled by the transmission pump, with oil not required by the high pressure pump. It's a closed center system, so the main pump will only use the oil that it requires to maintain pressure.

Do you have an issue where the hydraulics work ok sometimes, but get shaky and don't move other times? If so, you have a lack of adequate flow to the high pressure pump, or a leak in one of the high pressure circuits directly into the transmission - on my old JD300, I had this problem with the 3 point hitch valve.