Third Hose on PT-425 Rear Wheel Motor?

[Clumber]

Thanks Ponytug, for the explanation. Do older PTs have this third line? If not I wonder how the older models made turns.

 

[Clumber]

ok i'll buy the "differential" idea.

That seems like a good explanation especially since Terry said it.

Yes, and I' sure Terry is busy updating all the CAD drawings to reflect the third hose.

 

[MossRoad]

We have already established that is is not a case drain. A case drain is a 3rd fitting on the motor housing. That is tapped into the side of a fitting external to the motor housing.

That 3rd hose between your two rear wheel motors most likely was added to equalize pressure or relieve pressure or build pressure or do some other magic between the two series circuits.

I think the way my PT425 is set up is the left rear wheel and right front wheel are in series. The left front and the right rear are in series. That makes up the two series circuits( if the wheels on the same side of the tractor were in series, they would skid when turning, I would think, but could be mistaken).

Then those two series circuits are connected in parallel.

You can see that in the schematic posted in post 1 of this thread.

 

[J_J]

We have already established that is is not a case drain. A case drain is a 3rd fitting on the motor housing. That is tapped into the side of a fitting external to the motor housing.

That 3rd hose between your two rear wheel motors most likely was added to equalize pressure or relieve pressure or build pressure or do some other magic between the two series circuits.

I think the way my PT425 is set up is the left rear wheel and right front wheel are in series. The left front and the right rear are in series. That makes up the two series circuits( if the wheels on the same side of the tractor were in series, they would skid when turning, I would think, but could be mistaken).

Then those two series circuits are connected in parallel.

You can see that in the schematic posted in post 1 of this thread.

david,

I know this is an old post, but is your machine different than this one.

I have the one side in red and the other side in green, and it looks like the left side is in series and the right side is in series.

The left side is in parallel with the right side.

They both should get the same flow in GPM's, and each motor will develop it's own pressure/torque.

That third line is not a case drain.

Don't even know the purpose of it. Maybe to bleed off pressure, or steal some GPM's from the other side.

That fitting is apparently made up special by PT. Don't know why they did not use a tee.

The S is the starting point and the split.

 

[KentT]

david,

I know this is an old post, but is your machine different than this one.

I have the one side in red and the other side in green, and it looks like the left side is in series and the right side is in series.

The left side is in parallel with the right side.

They both should get the same flow in GPM's, and each motor will develop it's own pressure/torque.

That third line is not a case drain.

Don't even know the purpose of it. Maybe to bleed off pressure, or steal some GPM's from the other side.

That fitting is apparently made up special by PT. Don't know why they did not use a tee.

The S is the starting point and the split.

My guess is that the third line provides the equivalent of a differential, providing more volume to the outside wheelmotors in turns.

 

[MossRoad]

I'll have to look but as I recall, no, I only have two lines to each wheel motor. I'll Chaco after the 500

 

[KentT]

I'll have to look but as I recall, no, I only have two lines to each wheel motor. I'll Chaco after the 500

Be willing to bet that yours does not -- mine doesn't, and AFAIK, they were likely built only a few months apart...

 

[MossRoad]

I checked and my 2001 model year PT425 only has two (2) hoses attached to each wheel motor.

 

[J_J]

David, what about the wheel motor coupling.

Is yours like the picture I posted or is your like you said earlier. Left front and right rear?

 

[MossRoad]

As I recall, mine are left front and right rear in series. Right front and left rear in series. And both of those circuits are in parallel. There is no third hose anywhere.