stray
Platinum Member
- Joined
- Jan 18, 2004
- Messages
- 710
- Location
- east TN
- Tractor
- Power-trac 422 2003 model and 428 January 2015 model
As to the best of my knowledge and investigation the only time that hydraulic oil passes through the oil cooler is when the tram motors are running. If someone knows different please let us know how it does or even could. It may be that some of the PTs are set up different but my is a 2003 PT422.
Ok the large motor or tram motor is in the front (of my 422). It is a piston pump that has a swash plate. The plate tilts one way to go forward the other to reverse. When the plate is not tilted the pistons are not displacing any fluid so you do not need any relief valves or dump valves in this circuit. You are not moving any fluid so none goes through the cooler.
Now with this said when you start up a hill and you try to go forward pushing down on the peddle and the PT is not going forward what is happing is that you are having fluid bypassing (leaking back through) the tram pump pistons. This is normal and can get worse as the pump wares. If you push the peddle further down and ask the pump to displace more fluid then the pump over comes the leakage and the PT goes on up the hill or the motor dies. I guess another thing that could happen is the tires could spin but we all know that doesn't happen
Another circuit on the PT is the (I will call it the cylinder circuit). This is ran by the smallest gear pump and it drives every one of the cylinders on the PT. I am not sure that it is by passing through the by pass valve all the time when cylinders are not being used or not. I think it is?
The third circuit is the PTO circuit. It flows at all times. If you turn the PTO switch on, a valve is closed and the only escape for the flow is out the PTO circuit to a mower (or what ever) or through it's by pass valve.
I hope this information is correct and will be useful to someone. I know I would like to have know this when I first started PTing. Thanks guys and keep up the good posts. I don't post as often as I once did but rest assured I will be reading each and every post posted.
Ok the large motor or tram motor is in the front (of my 422). It is a piston pump that has a swash plate. The plate tilts one way to go forward the other to reverse. When the plate is not tilted the pistons are not displacing any fluid so you do not need any relief valves or dump valves in this circuit. You are not moving any fluid so none goes through the cooler.
Now with this said when you start up a hill and you try to go forward pushing down on the peddle and the PT is not going forward what is happing is that you are having fluid bypassing (leaking back through) the tram pump pistons. This is normal and can get worse as the pump wares. If you push the peddle further down and ask the pump to displace more fluid then the pump over comes the leakage and the PT goes on up the hill or the motor dies. I guess another thing that could happen is the tires could spin but we all know that doesn't happen
Another circuit on the PT is the (I will call it the cylinder circuit). This is ran by the smallest gear pump and it drives every one of the cylinders on the PT. I am not sure that it is by passing through the by pass valve all the time when cylinders are not being used or not. I think it is?
The third circuit is the PTO circuit. It flows at all times. If you turn the PTO switch on, a valve is closed and the only escape for the flow is out the PTO circuit to a mower (or what ever) or through it's by pass valve.
I hope this information is correct and will be useful to someone. I know I would like to have know this when I first started PTing. Thanks guys and keep up the good posts. I don't post as often as I once did but rest assured I will be reading each and every post posted.