Clark transmission Charge Pressure problem

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need your help guys, we're fighting with transmission problem on a peice of railyard equipment known as a swingloader or swingmaster or speedswing.

Every once in a while there is no transmission charge pressure on startup. Doesn't seem to care if it's inside a building or outside in the cold. Clark transmission with an external torque converter in a housing and an external converter charge pump. (gear pump) There's a converter pressure gauge in the cab, it shows no pressure when this happening. Overfilling the trans seems to make it better. We've replaced the charge pump, all the hoses involved, and the converter pressure regulator valve.
Nothing helped.

Anybody run into this before or have an ideas? :Banghead

 

[excavator]

Do you know what series the torque converter and the transmission are? I have several Clark manuals that I could check if I know the model numbers.

 

[motrack]

How about a plugged suction screen? I am sure there is one in the system before the charge pump.

 

[OFF]

Do you know what series the torque converter and the transmission are? I have several Clark manuals that I could check if I know the model numbers.

Trans - model R28662-23, serial #GUSA21896
Torque - model C273.5199, serial #GUSA210890

 

[OFF]

How about a plugged suction screen? I am sure there is one in the system before the charge pump.

the suction line goes into the transmission sump near the bottom. Didn't see a screen with the hose off.
Don't get a lot of vaccum on the suction hose with the engine running either. Very slight vacuum felt on when your hand is placed over the end of the hose.

 

[motrack]

Was the charge pump replaced with a new or rebuilt one? Was it removed from something else and installed on this machine?

 

[grandpa]

the suction line goes into the transmission sump near the bottom. Didn't see a screen with the hose off.
Don't get a lot of vaccum on the suction hose with the engine running either. Very slight vacuum felt on when your hand is placed over the end of the hose.

Is this suction a rubber hose? I had a suction hose with a loose flap of rubber on the inside of the hose. Caused me fits for quite a while.

 

[excavator]

On a C-270 series conveter there is a Safety Valve located on the bottom side of the regulating valve assembly. One of listing for low converter out pressure is this valve sticking. I know you said you replaced the pressure regulating valve but it might be worth another check. When you say "overfilling seems to help", that make me think maybe a suction line problem in the transmission itself. All my 28000 series manuals are the HR model, 1 piece torque and trans so I don't have any schematics for that. Hope this helps, I've never worked on any, just have some manuals.

 

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Was the charge pump replaced with a new or rebuilt one? Was it removed from something else and installed on this machine?

a brand new genuine Clark pump was installed, identical to the one we replaced.

 

[OFF]

Is this suction a rubber hose? I had a suction hose with a loose flap of rubber on the inside of the hose. Caused me fits for quite a while.

It had a #16 fabric braid suction hose. We replaced it with a single braid #16 hydraulic hose. Cut the end off the old hose and looked inside it, didn't see a flap.

:Banghead

 

[OFF]

On a C-270 series conveter there is a Safety Valve located on the bottom side of the regulating valve assembly. One of listing for low converter out pressure is this valve sticking. I know you said you replaced the pressure regulating valve but it might be worth another check. When you say "overfilling seems to help", that make me think maybe a suction line problem in the transmission itself. All my 28000 series manuals are the HR model, 1 piece torque and trans so I don't have any schematics for that. Hope this helps, I've never worked on any, just have some manuals.

I'll take a closer look at that valve. When the pump finally does prime and starts to pump, the pressure is higher than normal. The gauge is pretty much maxed out.

 

[excavator]

Go to www.emeraldwest.com/parts/manuals.html. They have parts breakdown pics of Clark transmissions and converters. Check out the 28000 series transmission section. Go down to R & HR model 3 & 6 speed long drop. Does this look like what you have? TheC270 converter section also shows the pressure regulator valve housing with the safety valve. Hope this helps.

 

[oldseabee]

The suction screen is located behind the drain plug. Pull the plug and there is the screen. There is an internal pipe from the hose connection to the back side of the suction screen, on rare occasion this has developed a leak, either a crack or at the connection behind the hose. If it is a crack, some times you can overfill a little to cover the crack, but too much overfill can cause foaming due to the oil level getting up into the gear train. There is a case drain from the convertor back to the transmission sump and if the drain hose gets plugged or the lining comes loose, the convertor will not drain back properly and the oil level in the trainsmission will get too low, or if the convertor has excess internal leakage it can overcome the drain back line and have the same result.

 

[MOTOR POOL BILL]

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Did you ever work out the intermitent presure problem? I have a 1980 snow blower up here with the same symtoms. We are just about to replace the charge pump

 

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Did you ever work out the intermitent presure problem? I have a 1980 snow blower up here with the same symtoms. We are just about to replace the charge pump

Fingers crossed - so far, so good. We couldn't find anything wrong, what we ended up doing was making up a new pressure hose a little longer so it humped up above the outlet fitting of the charge pump. Thinking was to trap a little oil in there on shutdown so the pump would never be dry on start up.
It's been almost 2 weeks since it left the shop and the problem has not reoccured as yet.
We pulled the old charge pump apart, and didn't see much wrong with it at all for 3800 hrs. worth of wear & tear.

A big thanks to everyone who posted. You all helped greatly :drinkup

 

[carl83]

anyone know where I can get manuals for a clark 210 hb scraper