Good evening,
This is a question for those of you who have or had a JD 440A or similar skidder. I have the owners manual and Service Manual, but they have left me confused. Do I understand correctly that the transmission oil filter service light is activated by the engine oil pressure switch?
Thanks!
I'm amazed a light still works on a 440a. Must be a nice Skidder. I'm just guessing here as my old 440 didn't have those working lights. But I can't see the engine oil pressure affecting the trans. But maybe it is an oil pressure (same style) switch just on the trans to measure its return pressure.
(https://forestryforum.com/gallery/albums/userpics/18022/IMG_7801.jpeg?easyrotate_cache=1696806615)
Here is the statement from the owners manual
Interesting
I wonder if it's just sending voltage. That way the transmission knows the engine is running. But it would give you false trans filter indication if your engine is getting tired or the engine oil pressure switch is faulty.
I would imagine it is wired through the oil pressure switch so when you turn the key on warning lights come on so you can make sure all warnings lights are working.After engine is running light would get its signal from switch on transmission filter housing.
The manual statement could be read several ways. Maybe it is saying that don't expect the filter light to go off until the engine has run enough to build oil pressure. It doesn't necessarily mean that they are connected at all other than the transmission won't have pressure unless the engine is running.
I haven't found any confirmation of it, but I believe that the engine oil pressure drives the clutch engagement in this hookup. Until the clutch is fully pressurized and engaged, the transmission internals and associated fluid pump will not spin at the minimum rpm required to create proper operating pressure.
Thus if your oil pressure light is off and your transmission filter light is on, your filter is plugged and fluid in the passage after the filter is at low pressure.
What's interesting is can't find anywhere in the transmission fluid circuit where there is a sensor of any kind. I have the trans filter light. I have 12 volts at one lead. Presumably, the other lead (ground) is controlled by a pressure sensor. Found the oil pressure sensor and the terminal is busted off, but there is no wire in the area. I can run a wire easy enough, I just need to know what to hook it up to!