CLARK FORKLIFT IC102 Power Train Introduction TECHNICAL TRAINING MANUAL

IC102

Power Train Introduction

TECHNICAL TRAINING Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Copyrighted Material Intended for CLARK dealers only Do not sell or distribute

Contents About this class............................................................................................

About safety.................................................................................................

Section 1. Introduction to the Powershift Transaxle.................................

Powershift Transaxle Overview.......................................................

Section 2 Torque Converter.........................................................................

Converter Parts.................................................................................

How the Converter Multiplies Torque.............................................

Summary...........................................................................................

Related Problems..............................................................................

Section 3 Transmission................................................................................

How the Transmission Works...........................................................

Related Problems..............................................................................

Section 4 Hydraulic System........................................................................

Basic Hydraulic Principles................................................................

Force and Speed................................................................................

Figuring Hydraulic Force.................................................................

Hydraulic System Components........................................................

How the Hydraulic System Works...................................................

Overview............................................................................................

Transmission in Neutral...................................................................

Transmission in Forward..................................................................

Transmission in Reverse...................................................................

Clutch Pack Disengagement.............................................................

Pressw·e Regulator Valve.................................................................

Converter Relief Valve......................................................................

Transmission Control Cover.............................................................

Inching Valve and Inching................................................................

Modulator and Accumulator Valves.................................................

Solenoids............................................................................................

Forward and Reverse Pilot Valves...................................................

Cooling and Lubricating...................................................................

Summary...........................................................................................

Related Problems..............................................................................

Fluid Level.........................................................................................

Intake Screen.....................................................................................

Charge Pump.....................................................................................

Filter..................................................................................................

Pressure Regulator Valve.................................................................

Converter Relief Valve......................................................................

Converter...........................................................................................

Cooler.................................................................................................

Accumulator Valve ...........................................................................

Clutch Packs......................................................................................

Hydraulic Lines.................................................................................

Section 5. The Drive Axle............................................................................

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Power Train Introduction page 1

Ring and pinion gear............................................................................

The Differential....................................................................................

How the Differential Works.................................................................

Drive Axle Problems.............................................................................

Section 6 Troubleshooting...............................................................................

Before You Troubleshoot......................................................................

Preliminary Steps.................................................................................

Step 1. Clean the Truck and Powershift Transaxle............................

Step 2. Check the Engine.....................................................................

Step 3. Check the Transmission Oil Level..........................................

Step 4. Check for Visible Leaks and Check Linkage Conditions.......

Step 5. Check Inching Pedal Free Play...............................................

Stall Tests.............................................................................................

Pressure Checks....................................................................................

Step 1 Check the Transmission Charge Pump Pressure....................

Step 2 Pressure Check the Forward and Reserse...............................

Step 3 Pressure Check the Converter..................................................

Summary...............................................................................................

Section 7. Easy Reference Troubleshooting...................................................

Lack of power........................................................................................

Truck will not move in either direction...............................................

Truck moves in one direction and creeps in that direction in neutral but stalls when shifted to opposite direction.....................

Truck moves slowly in both directions at wide open throttle............

Slow or erratic clutch engagement......................................................

Low clutch pressure and slow engagement at idle.............................

Low clutch pressure with normal clutch leakage...............................

Low clutch pressure with excessive clutch leakage............................

High clutch pressure............................................................................

Transmission overheats......................................................................

Truck has full power and transmission overheats..............................

Continuously high oil temperature......................................................

High stall speed....................................................................................

High stall speed with tinny sound.......................................................

Low stall speed......................................................................................

Low transmission charge pump output...............................................

Low flow through cooler with low converter in pressure....................

Low flow through cooler with high converter out pressure................

Suction line taking in air.....................................................................

Noise in converter.................................................................................

Converter bas broken straps or disc....................................................

Oil in engine flywheel housing.............................................................

Noise or noisy turn............................................................................... ©Copyright Clark Material Handling Company 1990 Revised 1998

Power Train Introduction page 2

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About this Class

This class and manual will introduce you to the Powershift Transaxle. When you have completed the class and passed the test, you will know how the components of a typical Powershift Transaxle work and how to troubleshoot them.

The power train consists of three units: torque converter, transmission, and drive axle (also called "power axle" or "Transaxle"). The power train receives energy from the en­ gine and converts it through the torque converter and transmission into energy to power the drive axle and wheels.

A hydraulic system plays a vital role in the functioning of the torque converter, transmis­ sion, and drive axle. In Clark equipment, the converter, transmission and hydraulic sys­ tem function as a unit called the Powershift Transmission. In smaller units, the drive axle is considered a part of the Powershift Transmission and the whole unit is referred to as the Powershift Transaxle.

Note To avoid confusion, the terms "Powershift Transaxle" or "Powershift Transmis­ sion" will always refer to the whole unit, while the term "transmission" will refer only to the part of the Powershift Transaxle that contains the gears and clutches.

Because the converters, transmissions, hydraulic systems and drive axles on different models will vary, this class will discuss a typical Powershift Transaxle. Other classes will cover how to troubleshoot and rebuild specific transmissions and transaxles in greater detail.

Whenever you are working on a transmission or transaxle, always consult the unit's appropriate service manual.

The first five sections of this manual will show you how the components of the Powershift Transaxle work. You will also be introduced to some problems that might occw· if these components malfunction.

The sixth section will teach you the basic approach to troubleshooting the Powershift Transaxle. A reference guide is included at the end of this book to assist you in trouble­ shooting.

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Power Train Introduction page 3

About Safety

The following messages may be used to emphasize important information: Note This message is used when special information, instructions or identification is required relating to procedures, equipment, tools, pressures, capacities and other special data.

Important This message is used when special precautions should be taken to ensure a correct action or to avoid damage to or malfunction of the truck or a component.

CAUTION This message is used as a reminder of safety practices which can result in personal injury if proper precautions are not taken.

WARNING This message is used when a hazard exists which can result in injury or death if proper precautions are not taken.

DANGER

This message is used when an extreme hazard exists which will result in death or serious injury if proper precautions are not taken.

Please observe the following safety messages when troubleshooting a transmission or transaxle. We want you to be sw·e that you troubleshoot in a manner that is both safe for you and safe for the people around you.

CAUTION Hot coolant, steam, or transmission fluid can cause severe burns. If pos­

sible, avoid touching or working on any system until it has an opportunity to cool. Be careful that you do not burn yow·self with hot transmission fluid. Also, be careful that you do not burn yourself with any steam or coolant escaping from the radiator. Avoid touching hot parts. Protect your arms by wearing long sleeved shirts buttoned at the wrists.

CAUTION Whenever possible, work with the engine turned off.

When you have to work with the engine running, be sure to observe the following safety procedures: • Place the transmission in neutral.

• Put the parking brake on.

• Lower the forks onto the floor.

• Double block the wheels.

CAUTION Moving parts can cause extensive injury!

Keep hands, arms, and clothing away from rotating parts. Never wear loose clothing. Tie back long hair. Avoid wearing rings, watches and jewelry.

CAUTION Transmission fluid is hot and pressurized. Never open a port with the

engine running. The force of the transmission fluid as well as its heat can cause bodily harm.

Power Train Introduction page 4

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Section 1. Introduction to the Powershift Transaxle This section is designed to acquaint you with the functioning's of a Powershift Transaxle and the safety precautions that should be taken when working on it. Other sections of this manual will cover these functions in greater detail.

Powershift Transaxle Overview

Clark lift trucks owe a large share of their excellent reputation to the Powershift Transaxle.

The Powershift Transaxle is dependable and performs well in high-cycle, heavy-duty operations.

The Powershift Transaxle consists of four units: •Torque Converter •Transmission •Transmission hydraulic system • Drive axle.

The torque converter (often referred to as "converter") takes energy from the engine's flywheel and increases it as needed by multiplying torque.

The converter transfers this energy to the transmission. Most Powershift Transaxles have two power-shifted packs: forward and reverse. A few transmissions will have an optional four-pack system: high and low in addition to forward and reverse.

The drive axle transmits power to the wheels and differentiates the speed of the wheels.

Both the converter and transmission are hydraulically operated (or fluid operated) sys­ tems that use transmission fluid (sometimes referred to as "oil") to increase transmission power as well as to cool and lubricate the Powershift Transaxle's mechanical parts.

Throughout the years, Clark has produced numerous types of transmissions. The TA 12, TA18, and the TA 30 are examples of transmissions designed by Clark Material Handling Company.

Because of the different types of transmissions and transaxles, how to troubleshoot, tear down, and rebuild specific transmissions and transaxles will be discussed in other classes.

This class will focus on how a typical Powershift Transaxle works and how to trouble­ shoot it.

This class will use the TA18 transmission as an example.

Note Even though most transmissions will have the same parts, the names and locations of these parts may vary according to models. Always be sure you consult the appropriate manuals when you troubleshoot a transmission.

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Power Train Introduction page 5

Section 2 Torque Converter

In this section you will learn what the torque converter is, how its parts operate to mul­ tiply torque, and what problems might arise with the converter and its parts.

The torque converter is a fluid operating device that takes the place of a conventional clutch and multiplies torque. The torque converter is driven by its driving disc which is bolted to the engine flywheel. The converter receives its power from the flywheel, in­ creases it when needed, and transfers it to the transmission.

The torque converter has four advantages: • It absorbs shock to prolong the power train's life.

• It permits the transmission to quickly change gears-even under heavy loads.

• It multiplies torque and delivers smooth power which creates more driving force at the wheels.

• It requires no periodic adjustments and does not use complicated components.

Though the torque converter is not repairable, the converter plays such an important part in the functioning of the fork truck that we will cover its operation in detail.

Torque Converter Converter Parts

The torque converter consists of three parts: impeller, turbine, and stator. These three parts and the hydraulic fluid in them function as one unit to multiply torque from the engine.

Impeller The impeller is driven by the engine in a clockwise direction (as viewed from the front of the engine). The impeller and the cover welded to it form the torque converter's outer housing. The housing, which is completely filled with transmission fluid, contains the stator and turbine. A properly functioning impeller turns whenever the engine is turning and acts like a hydraulic pump.

Power Train Introduction page 6

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Turbine The turbine is enclosed in the torque converter and is splined to the input shaft of the transmission. It is driven by fluid thrown from the impeller. Thus, the turbine transmits horsepower and torque from the engine and impeller to the transmission.

Stator

The stator, which is mounted on a one-way sprag clutch, is also enclosed in the torque converter. The stator and sprag clutch are mounted on the stationary stator support shaft which is bolted to the transmission case. The sprag clutch contains tiny wedges which allow the stator to rotate only in the direction that the impeller rotates. When fluid hits the stator and tries to turn it in the opposite direction, the wedges lock the stator to the stator support shaft which prevents any reverse rotating. When the stator locks to the shaft, the converter begins to multiply torque.

Adaptor

Turbine

Drive

Housing

Plate

Clutch Shaft

Torque Converter How the Converter Multiplies Torque

You can get a better understanding how the converter multiplies torque by tracing the flow of fluid from impeller to turbine, turbine to stator, and stator to impeller from the time the engine is started until the converter no longer multiplies torque.

I.When the engine is started, the flywheel turns the impeller. When transmission fluid in the converter hits the impeller's cup blades, the fluid changes direction. The impeller's speed causes the transmission fluid to be hurled from its blades onto the turbine blades forcing them to turn. The fluid flows through the turbine and is thrown from it at high speeds.

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Power Train Introduction page 7

2.The fluid then enters the stator and tries to turn it in a direction opposite of the impeller's.

Since the sprag clutch locks and prohibits movement opposite impeller rotation, the fluid flows at high speed off the curved stator blades, changes direction, and races out of the stator in the same direction the impeller is turning. When this fluid hits the impeller, it creates torque.

3.The fluid, still travelling at high speed, reenters the impeller. The energy of the fast moving fluid is added to the energy of the tw·ning flywheel creating more force to drive the impeller blades. This increased energy represents increased torque.

4.The torque converter produces a maximum torque multiplication in most models rang­ ing from 2 to 1 to more than 3 to 1. The stall point of the converter occurs when resistance is greater than the energy produced by the torque converter and engine. When the con­ verter reaches its stall point, the impeller will be turning, but the turbine will not.

Note The stall point is the fixed rpm that must be achieved so that the truck will be able to operate at maximum torque when pushing loads and climbing ramps.

When the stall point is reached, the truck will not be able to overcome resistance and will not move.

5. When enough torque is developed by the engine and converter, the turbine begins to rotate. This rotation tw·ns the turbine and the input shaft that drives the transmission components.

6.Torque multiplication gradually tapers off as turbine speed approaches impeller speed and becomes 1 to 1 when the tm·bine rotates at about 90% of the impeller's speed. At this point, the converter is no longer multiplying torque.

7.When the turbine rotates faster than 90% of the impeller's speed, the fluid leaving the turbine hits the back faces of the stator blades. The one-way clutch now permits the stator to freewheel (turn with the impeller and turbine). At this point, the converter is an efficient fluid coupling and remains one as long as turbine speed remains greater than 90% impeller speed.

A fluid coupling occurs whenever the truck encounters no resistance. This can happen when the engine is idling in neutral or when it is cruising at high speeds. Once resistance carrying a heavy load, or trav­ is met (such as going into gear, accelerating rapidly, elling up a grade), extra torque is needed. The resistance causes the turbine to drop below 90% of the impeller's speed and the converter begins to create more torque to overcome the resistance. The more resistance that is encountered, the more torque that is required for the truck to perform.

From the time the turbine is not rotating to the point where the converter becomes a fluid coupling (when the tm·bine rotates above 90% of the impeller's speed), the converter acts as an infinitely variable, fluid-operated transmission based on resistance. Whenever the truck encounters resistance, the converter will multiply the needed amount of torque to overcome this resistance as long as it falls within the 1 to 1 and 4 to 1 boundaries.

Power Train Introduction page 8

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