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CLARK TORQUE CONVERTERS

Theory of Operation

What do you do when your Torque Convertergoes "CRUNCH" instead of running properly?Well that depends. It might be a simple repair ...or you might have to take it apart down to thelast washer.

In any case, it's a good thing to know just how aTorque Converter works.

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They are called hydrostatic and hydrodynamicsystems.

3M 8411 CGAC

A Torque Converter is a device which transmitsforce and motion from an engine to a transmis­sion by means of hydraulic oil. There are reallyonly two kinds of systems that transmit energyhydrau Iically.

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Hydrostatic systems work on the principle that aconfined liquid will transmit pressure.

It is the systems used in construction machineryfor brakes, steering, implement controls and soon.

A fluid coupling is something like the two fans.The _fan on the right is called an impeller and itIS dnven by the engine.

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Hydrodynamic systems work on the principle •that a fluid in motion has force. For instance ifyou look at two fans facing each other and oneis plugged in and the other isn't, you would seethat the electrically driven blades were forcingair toward the bladesof the unpluggedfan. Thisflow of air has force which makesthe bladesofthe unpluggedfan rotate.

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As the impeller rotates, oil in the impeller flowsoutward becauseof centrifugal force.

A Torque Converter operateson the sameprinci­ple as the fluid coupling but usesone additionalmember called a stator .

This outward flowing oil leavesthe impeller andstrikes the blades of the second fan called aturbine, so you can seethat it is the force of thisflowing oil that causes the turbine to rotate.This fluid coupling is complete and energy istransmitted from one member to the otherthrough oil flow.

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Why a stator you may ask. Well simply to multi­ply Torque.

The impeller is connected to the engine flywheel and rotates whenever the engine is on.The stator is mounted on a support and does notrotate. The turbine mounted on the turbineshaft is connected to the transmission throughgearing and a prop shaft. Here is how these threemembers the impeller, the turbine and the statorwork together to multiply Torque.

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Clark Converters can multiply Torque asmuch asthree-to-one (3 to 1). If the engine develops 100foot pounds, the converter can increase theTorque to 300 foot pounds all because of thestator. The fluid coupling has no stator and cannot multiply Torque.

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Suppose that your machine is traveling on asmooth flat surface with no load and the engineis turning at 2000 RPM. The impeller, becauseit is connected directly to the engine, is alsoturning at 2000 RPM and with no load, the tur­bine matches that 2000 RPM speed. With theturbine and impeller rotating at the samespeed,each create the samecentrifugal force .

Now suppose that your machine is placed undera load which reduces the turbine speed to 1000RPM. The engine and impeller will still turn at2000 RPM. Now the turbine has only about halfthe centrifugal force of the impeller. As you cansee, this would cause a flow of oil from theimpeller through the turbine.

The oil which trys to leave the impeller is coun­teracted by the oil which trys to leave the tur­bine. The result is that both members and the oilrotate asone mass.

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But even after the oil flows through the turbine,it is still moving rapidly and has force. This iswhere the stator comes in.

If enough load is placed on the machine to stallthe turbine, the turbine would lose all centrifu­gal force

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The stator redirects the oil flow so that the oilstrikes the blades of the impeller in the samedirection as the impeller is rotating and that iswhat multiples Torque. In this case about two­to-one (2 to 1). Now let us take it one stepfurther.

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but the impeller would continue to turn atengine speed and would continue to generatecentrifugal force.

When both members are rotating at the samespeed,Torque multiplication is zero "0". Whenthe turbine rotates at half the impeller speed,the Torque is multiplied two-to-one (2 to 1).When the turbine is topped or almost stalled, theTorque is multiplied three-to-one (3 to 1) andthis Torque multiplication is infinitely variablebetween one-to-one (1 to 1) and three-to-one (3to 1).

Becausethere is more force available in the formof increasedoil flow, the Torque multiplicationis now about three-to-one (3 to 1). You couldsum it up this way.

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Of course, there are other factors that effectTorque multiplication besides the relative speedsof the turbine and impeller - like the number ofblades on each of the three members and theangle at which these blades are mounted.

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Factors of torquemultiplication

I~~~~of~klrNumber of blades in stator,impeller and turbine.

Angle of blades in stator,impeller and turbine.

Like all other man-made machinery, the Torque 0..•../Converter is not 100 per cent efficient. Becausethe members are not mechanically connected,there is some oil slippage and the result is heat.

By adding a pump and an oil cooler, excessheatcaused by lost motion and friction can be re­moved from the converter. The pump is used tosupply the converter with cool filtered oil and toforce hot oil from the converter through the oil ';'" ,/:.cooler. ..

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The oil cooler receiveshot oil from the conver­ter, cools it and returns it to the system.Coolersalso create some back pressurewhich helps tokeep the converter fu II of oi I. To understandhow back pressurehelps to keep the converterfull, consider this example.

But if the same container receiving exactly thesame amount of flow is fitted with a smallerdrain hole, the oil level in the container will behigher. The container can be compared to aTorque Converter and the smaller hole to the re­striction causedby the cooler.

If a container with a drain hole is receiving aconstant flow of oil, the level of oil in thecontainer will be near the top of the drain hole.

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Some converters are also fitted with a downstream regulator valve. The oil leaving theconverter must push the down stream regulatorspool against a spring. This creates back pressurewithin the converter and keeps it full of oil.

Other models of Clark Converters do not havepressure relief valves. However, the transmissioncontrol valve contains a safety valve which servesexactly the same function.

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All C270 Converters have a relief valve. If oilflow is restricted, the valve will open to relieveexcesspressure.

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Clark Torque Converters have several advan­tages.They absorb shock which prolongs powertrain life .

They multiply Torque and deliver powersmoothly which results in more driving force atthe wheels.

They permit the use of a power shift transmis­sion which can permit quick gear changingevenunder load.

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They require no periodic adjustments

Now here are some common Torque Converterproblems and trouble-shooting procedures.

First of all, it is essential to remember that theconverter charging pump, the Torque Converter,converter oil cooler, the transmission and theconnecting lines must be considered as one com­plete system. A fault in one component cancause a problem to appear in another compo­nent.

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and they do not use complicated components .

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Remember, that related components requirerelated checks.

Remember that the Torque Converter and trans­mission use the same transmission fluid. Makecertain that the transmission fluid used in themachine is as specified in Clark's Operator andMaintenance Manuals and that the transmissionoil level is correct.

Here are some of the possible causes for anoverheating Torque Converter: operating themachine in too high of a gear ratio, a faultytemperature gauge, low oil level in the transmis­sion,

One of the most common problems with aTorque Converter is overheating. There aremany causes for an overheating converter severalof which are not the fault of the converter. Donot remove the converter and dive into a com­plete disassembly before checking all the possi­bilities.

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an overheating engine, low charge pump flow, aconverter drain line plugged,

Before condemning a converter, be sure to in­stall gauges and measure pressures as describedin the Maintenance or Shop Manual. Many timesa problem which appears to be the fault of theconverter is not the converter at all but the faultof a related component.

Always refer to the proper shop manual forspecifications and disassembly, assembly pro­cedures.

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a converter oil cooler plugged, a restriction in •the cooler lines, excessive converter leakageandexcessivetransmission leakage.

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