ATTENTION ! Resisdent Hydraulic expert !!

[BigAl]

Ok ! I know we have a couple of good old boys on here who are the FF resident Hydraulic experts . I sure as hell ain't one of them .

I got a problem .... I think . It is on my KT7 Hydrostatic transmission . I had two transmissons , side my side , one to drive each track . Theses are attached to the bell housing and sure look like they are gear driven to me ???? I have 2 hydraulic oil ports in each transmission .I assume they are a enter and exit port I assume this must be for keeping the Hydrostatics cool ????? Why are these called Hydrostatic transmissions if there power is off the flywheel of the motor ??? Also and this is my main corcern , the hydraulic oil goes through my body tilt control valve and then as it returns to the tank a tee branches off to the transmissions. ???? Is this Right ????? It seems the oil should branch before going to the control valve ???

 

[DaveNay]

Ok ! I know we have a couple of good old boys on here who are the FF resident Hydraulic experts . I sure as hell ain't one of them .

I got a problem .... I think . It is on my KT7 Hydrostatic transmission . I had two transmissons , side my side , one to drive each track . Theses are attached to the bell housing and sure look like they are gear driven to me ???? I have 2 hydraulic oil ports in each transmission .I assume they are a enter and exit port I assume this must be for keeping the Hydrostatics cool ????? Why are these called Hydrostatic transmissions if there power is off the flywheel of the motor ??? Also and this is my main corcern , the hydraulic oil goes through my body tilt control valve and then as it returns to the tank a tee branches off to the transmissions. ???? Is this Right ????? It seems the oil should branch before going to the control valve ???

A hydrostatic transmission takes the mechanical input from the engine, and converts it to a variable flow hydraulic circuit. The rate of flow is contolled by a swash plate inside the trans, that will have some sort of external linkage. That linkage is then connected via rods (usually) to your foot or hand controls. The two ports on your transmission(s) are the supply and return lines for the hydraulic motors somewhere on the track assemblies. The hydraulic motor will take the variable flow hydraulic fluid and convert it to rotary mechanical motion, thus driving the tracks. Many times, the hydrostatic circuits are completely isolated from the remaining hydraulics due to the variable flow in the circuit (you wouldn't want your FEL to be dependent on the transmission), and there is a third, constant displacement pump that handles those tasks. If there are only two ports on your transmissions, then the system is probably completely isolated, however if there is a third port, then only the pressure side is isolated, and there is a common resevoir someplace.

 

[BigAl]

Ok I understand that . These two transmissions mount by a short ujoint directly to the right angle gear drives that hook to the track spocket . There is no other pumps or motors !!!!????????? Should not these me call automatic transmissions ??????

Ill post a couple pictures of these two Hydraulic transmissions . This is it . there is not anything else to this drve system .

 

[DaveNay]

Ok I understand that . These two transmissions mount by a short ujoint directly to the right angle gear drives that hook to the track spocket . There is no other pumps or motors !!!!????????? Should not these me call automatic transmissions ??????

Ill post a couple pictures of these two Hydraulic transmissions . This is it . there is not anything else to this drve system .

Here's my guesses then....

Purple box is the two hydrostatic pumps, as evidenced by the levers to control the swash plates. Yellow is the hydraulic motors driving your tracks. It looks like they merged the pumps and the motors into a single assembly, with the plumbing all internal. What does the assembly in the green box do? Looks like some sort of link between the two drives.

This is not an automatic transmission becuse you still have all the benefits of a hydro, such as revering flow, and no meshing gears. An automatic trans only has the torque converter as a means of de-coupling the mechanical drive at low RPM, and not stalling the engine.

 

[DaveNay]

There is no other pumps or motors !!!!?????????

Where does the pressure for the body cylinders come from? The "T" between the body control valve and the tank is probably the tank return line from the transmissions...."from" the transmissions, not "to" the transmissions.

 

[BigAl]

I have a lockable lever between the seats that hooks to this and raises the linkage bar up ,pulling up the pluger on each transmission with it and the prior owner said this was to change the speed from hi to lo . I guess they are similar to what they have on tractors so they can have a high and low torque .


It makes sense what you say, so I guess that the oil ports are just a supply and return line then??? Should the supply oil line to the transmissions be installed in the return line to the tank as it was, or should I pull a direct oil hose to the transmission directly from the hydraulic tank so I have unrestricted oil flow to the transmissions ???

 

[BigAl]

Where does the pressure for the body cylinders come from? The "T" between the body control valve and the tank is probably the tank return line from the transmissions...."from" the transmissions, not "to" the transmissions.

It was located and branched off from the return line from the Tilt control valve . This is what is so confusing to me.

***Also I have a small pump on the motor for the tilt rams an that is where it gets its pressure .

 

[DaveNay]

It was located and branched off from the return line from the Tilt control valve . This is what is so confusing to me

Where does the supply line for the tilt control valve go?

 

[BigAl]

Picture of Hydraulic body tilt pump..

 

[BigAl]

Sorry ,I misread the post . Hydraulic pressure for the Body tilt control is supplied by a small pump on the motor . see prior picture

 

[DaveNay]

Sorry ,I misread the post . Hydraulic pressure for the Body tilt control is supplied by a small pump on the motor . see prior picture

Ahhh...OK then. The "T" you are concerned with seems like it is on the tank side of the system, and is just a plumbing decision made by whoever designed the system. I would guess you could keep the "T", or plumb all three pumps directly back to the tank, and it would make no real difference.

 

[BigAl]

Thank You !!! I am sorry for not being more Hydraulic smart about this . I just wasnt sure and it is a bear to get to these lines once they are installed . Thanks for explaining how this system works , It makes sense now . I did notice they also had a one way check valve installed in the line . Can you tell me why ?

 

[DaveNay]

Thank You !!! I am sorry for not being more Hydraulic smart about this . I just wasnt sure and it is a bear to get to these lines once they are installed . Thanks for explaining how this system works , It makes sense now . I did notice they also had a one way check valve installed in the line . Can you tell me why ?

Where was the check valve installed, and which direction did it allow flow?

 

[BigAl]

Where was the check valve installed, and which direction did it allow flow?

It was installed in the return line from the body tilt control valve and flow direction was toward the tank . I can't remember it it was before or after the tee for the transmission supply line . I can go through my old pictures and know for sure if need be .

 

[DaveNay]

It was installed in the return line from the body tilt control valve and flow direction was toward the tank . I can't remember it it was before or after the tee for the transmission supply line . I can go through my old pictures and know for sure if need be .

Sounds like some sort of protection for the body control valve. When driving at higer speeds, the transmissions probably have pretty high pressure in the tank return line, and without the check valve, there would be pressure at the tank port of the body valve. Depending on the configuration of the body valve, this might cause the body to raise or lower while driving.

 

[BigAl]

Thank You !!!! This is why I love this site so much . Ok your now a honorary member of my Kristi Kat klub (KKK) and i'll buy the beer !!!

 

[DaveNay]

Thank You !!!! This is why I love this site so much . Ok your now a honorary member of my Kristi Kat klub (KKK) and i'll buy the beer !!!

 

[BigAl]

Can anyone tell me which oil port in this picture of my hydro drive is the supply and which is the return to the tank .I do not trust the way it was plumbed before . Does it matter ??? Thanks Allen

 

[DaveNay]

Can anyone tell me which oil port in this picture of my hydro drive is the supply and which is the return to the tank .I do not trust the way it was plumbed before . Does it matter ??? Thanks Allen

Al, Are there any markings on the transmissions that might indicate the manufacturer?

edit: Nevermind, I can read it in the picture "Funk Manufacturing"

 

[DaveNay]

Can anyone tell me which oil port in this picture of my hydro drive is the supply and which is the return to the tank .I do not trust the way it was plumbed before . Does it matter ??? Thanks Allen

OK...after much searching and deciphering, plus a little scotch and water and throwing a chicken bone over my shoulder, I am reasonably certain that port at the bottom of the housing (the elbow fitting) is the tank return, and the one on the side is the supply line. The check valves for the system are located behind the plugs that look like hex head bolts. Hopefully, there is also a 5, 10 or 25 micron filter somewhere in the system.

 

[BigAl]

You are my hero !
Thanks Allen