1998 GMC Sierra Pickup 2500 Repair Manual

FULL-SHE 1988-9£ r^PAIR MANUAL Covers all U.S. and Canadian models of Chevrolet/GMC Pick-ups, Sierra, Blazer, Tahoe, Yukon and Suburban; 2 and 4 wheel drive gasoline and diesel engines

Contents GENERAL INFORMATION AND MAINTENANCE 1-2 HOW TO USE THIS BOOK 1-2 TOOLS AND EQUIPMENT 1-4 SERVICING YOUR VEHICLE SAFELY 1 -5 FASTENERS, MEASUREMENTS AND CONVERSIONS 1-7 SERIAL NUMBER IDENTIFICATION 1-10 ROUTINE MAINTENANCE AND TUNE-UP 1-35 FLUIDS AND LUBRICANTS 1-46 TRAILER TOWING 1-47 JUMP STARTING A DEAD BATTERY 1-48 JACKING 1 -50 MAINTENANCE INTERVALS ENGINE ELECTRICAL 2-2 2-2 2-6 HIGH ENERGY IGNITION (HEI) SYSTEM 2-7 2-8 DISTRIBUTOR IGNITION (Dl) o Q SYSTEM FIRING ORDERS CHARGING SYSTEM STARTING SYSTEM SENDING UNITS AND SENSORS ENGINE AND ENGINE OVERHAUL 3-2 ENGINE MECHANICAL 3-56 EXHAUST SYSTEM 3-58 ENGINE RECONDITIONING 4-2 GASLINE ENGINE EMISSION 4-25 DIESEL ELECTRONIC DRIVEABILITY AND EMISSION CONTROLS CONTROLS 4-10 DIESEL ENGINE EMISSION CONTROLS 4-11 CARBURETED ELECTRONIC ENGINE CONTROLS 4-17 FUEL INJECTED ELECTRONIC ENGINE CONTROLS ENGINE CONTROLS 4-29 TROUBLE CODES 4-39 COMPONENT LOCATIONS 4-55 VACUUM DIAGRAMS FUEL SYSTEM 5-2 BASIC FUEL SYSTEM DIAGNOSIS 5-2 FUEL LINE FITTINGS 5-3 CARBURETED FUEL SYSTEM 5-10 THROTTLE BODY INJEC- TION (TBI) 5-14 MULTI-PORT FUEL INJECTION (MFI) 5-19 CENTRAL SEQUENTIAL FUEL INJECTION (CSFI) 5-22 DIESEL FUEL SYSTEM 5-26 FUEL TANK CHASSIS ELECTRICAL 6-2 UNDERSTANDING AND TROUBLESHOOTING ELECTRICAL SYSTEMS 6-7 BATTERY CABLES 6-7 SUPPLEMENTAL INFLATABLE RESTRAINT (SIR) SYSTEM 6-8 HEATING AND AIR CONDITIONING 6-12 CRUISE CONTROL 6-13 ENTERTAINMENT SYSTEMS 6-17 WINDSHIELD WIPERS AND WASHERS 6-19 INSTRUMENTS AND SWITCHES 6-22 LIGHTING 6-26 TRAILER WIRING 6-26 CIRCUIT PROTECTION 6-28 WIRING DIAGRAMS

Contents 7-2 MANUAL TRANSMISSION 7-9 7-4 CLUTCH 7-13 7-6 AUTOMATIC TRANSMISSION 7-16 7-8 TRANSFER CASE 7-19 8-2 WHEELS 8-4 C AND R SERIES 2WD FRONT SUSPENSION 8-14 V-SERIES 4WD FRONT SUSPENSION DRIVELINE SOLID FRONT DRIVE AXLE INDEPENDENT FRONT DRIVE AXLE REAR AXLE 8-18 K-SERIES 4WD FRONT . SUSPENSION 8-24 C3HD FRONT SUSPENSION 8-26 REAR SUSPENSION 8-30 STEERING SUSPENSION AND STEERING 9-2 BRAKE OPERATING SYSTEM 9-20 9-6 DISC BRAKES 9-12 DRUM BRAKES 9" 25 9-18 PARKING BRAKE FOUR WHEEL ANTI-LOCK BRAKE SYSTEM REAR WHEEL ANTI-LOCK (RWAL) BRAKE SYSTEM 10-2 EXTERIOR 10-5 INTERIOR 10-15 GLOSSARY 10-19 MASTER INDEX

SAFETY NOTICE Proper service and repair procedures are vital to the safe, re iable operation of all motor vehicles, as well as the personal safety of those performing repairs. This manual outlines procedures for servicing and repairing vehicles using safe, effective methods. The procedures contain many NOTES, CAUTIONS and WARNINGS which should be followed, along with standard procedures to eliminate the possibility of personal injury or improper service which could damage the vehicle or compromise its safety. It is important to note that repair procedures and techniquesM tools and parts for servicing motor vehicles, as well as the skill and experience of the individual performing the work vary widely. It is not possibles to anticipate all of the conceivable ways or conditions under which vehicles may be serviced, or to provide cautions as to all possible hazards tti£t may result. Standard and accepted safety precautions and equipment should be used when handling toxic or flammable fluids, and safety goggles or other protection should be used during cutting, grinding, chiseling, prying. or any other process that can cause mate/ial removal or projectiles. Some procedures require the use of tools specially designed for a completely satisfied that neither your personal safety, nor the performance of the vehicle specific purpose. Before substituting another tool or procedure, you must be will be endangered. Although information in this manual is based on industry sojurces and is complete as possibleat the time of publication, the possibility exists that some car manufacturers made later changes which could, inot be included here. While striving for total accuracy, the authors or publishers cannot assume responsibility for any errors, changes or omissions that may occur in the compilation of this data. PART NUMBERS Part numbers listed in this reference are not recommendat ences that can be used with interchange manuals and afterm ons by Haynes North America, Inc. for any product brand name. They are refer- rket supplier catalogs to locate each brand supplier's discrete part number. SPECIAL TOOLS Special tools are recommended by the vehicle manufacturer absolutely necessary, they are referred to in the text by the part priate part number, from your local dealer or regional distributo let. Before substituting any tool for the one recommended, o perform their specific job. Use has been kept to a minimum, but where lumber of the tool manufacturer. These tools can be purchased, under the appro- , or an equivalent tool can be purchased locally from a tool supplier or parts out- readl the SAFETY NOTICE at the top of this page. ACKNOWLEDGMENTS Portions of materials contained herein have been reprints Jwith the permission of General Motors Corporation, Service Technology Group. All rights reserved. No part of this book may be reproduce! ing photocopying, recording or by any information storage or transmitted in any form or by any means, electronic or mechanical, includ- >r retrieval system, without permission in writing from the copyright holder. While every attempt is made to ensure that the information in this manual is correct, no liability can be accepted by the authors or publishers for loss, damage or injury caused by any errors in, or omissions from, the information given.

HOW TO USE THIS BOOK 1-2 WHERE TO BEGIN 1-2 AVOIDING TROUBLE 1-2 MAINTENANCE OR REPAIR? 1-2 AVOIDING THE MOST COMMON MISTAKES 1-2 TOOLS AND EQUIPMENT 1-2 SPECIAL TOOLS 1-4 SERVICING YOUR VEHICLE SAFELY 1-4 DO'S 1-4 DONTS 1-5 FASTENERS, MEASUREMENTS AND CONVERSIONS 1-5 BOLTS, NUTS AND OTHER THREADED RETAINERS 1-5 TORQUE 1-6 TORQUE WRENCHES 1-6 TORQUE ANGLE METERS 1-7 STANDARD AND METRIC MEASUREMENTS 1-7 SERIAL NUMBER IDENTIFICATION 1-7 VEHICLE 1-7 ENGINE 1-7 TRANSMISSION 1-8 DRIVE AXLE 1-8 TRANSFER CASE 1-8 SERVICE PARTS IDENTIFICATION LABEL 1-10 ROUTINE MAINTENANCE AND TUNE-UP 1-10 AIR CLEANER 1-10 REMOVAL & INSTALLATION 1-13 FUEL FILTER 1-13 REMOVAL & INSTALLATION 1-13 PCVVALVE 1-15 REMOVAL & INSTALLATION 1-15 CRANKCASE DEPRESSION REGULATOR AND FLOW CONTROL VALVE 1-16 SERVICING 1-16 EVAPORATIVE CANISTER 1-16 SERVICING 1-16 BATTERY 1-16 PRECAUTIONS 1-16 GENERAL MAINTENANCE 1-16 BATTERY FLUID 1-17 CABLES 1-17 CHARGING 1-18 REPLACEMENT 1-18 BELTS 1-18 INSPECTION 1-18 ADJUSTMENT 1-18 REMOVAL & INSTALLATION 1-19 BELT ROUTING1-20 HOSES 1-23 INSPECTION 1-23 REMOVAL & INSTALLATION 1-23 CV-BOOTS 1-24 INSPECTION 1-24 SPARKPLUGS 1-25 SPARK PLUG HEAT RANGE 1-25 REMOVAL & INSTALLATION 1-25 INSPECTION & GAPPING 1-26 SPARK PLUG WIRES 1-27 TESTING 1-27 REMOVAL & INSTALLATION 1-27 DISTRIBUTOR CAP AND ROTOR 1-27 REMOVAL & INSTALLATION 1-27 INSPECTION 1-28 IGNITION TIMING 1-28 GENERAL INFORMATION 1-28 CHECKING & ADJUSTMENT 1-29 VALVE LASH 1-29 ADJUSTMENT 1-29 IDLE SPEED AND MIXTURE ADJUSTMENTS 1-30 CARBURETED ENGINES 1-30 GASOLINE FUEL INJECTED ENGINES 1-30 DIESEL ENGINES 1-31 AIR CONDITIONING SYSTEM 1-32 SYSTEM SERVICE S REPAIR 1-32 PREVENTIVE MAINTENANCE 1-32 SYSTEM INSPECTION 1-32 WINDSHIELD WIPERS 1-33 ELEMENT (REFILL) CARE & REPLACEMENT 1-33 TIRES AND WHEELS 1-33 TIRE ROTATION 1-33 TIRE DESIGN 1-34 TIRE STORAGE 1-34 INFLATIONS INSPECTION 1-34 FLUIDS AND LUBRICANTS 1-35 FLUID DISPOSAL 1-35 FUEL AND OIL RECOMMENDATIONS 1-35 OIL 1-35 FUEL 1-36 ENGINE 1-37 OIL LEVEL CHECK 1-37 OILS FILTER CHANGE 1-37 MANUAL TRANSMISSION 1-38 FLUID RECOMMENDATION 1-38 LEVEL CHECK 1-38 DRAINS REFILL 1-39 AUTOMATIC TRANSMISSION 1-39 FLUID RECOMMENDATIONS 1-39 LEVEL CHECK 1-39 DRAINS REFILL 1-39 TRANSFER CASE 1-40 FLUID RECOMMENDATIONS 1-40 LEVEL CHECK 1-40 DRAINS REFILL 1-40 FRONT AND REAR DRIVE AXLES1-40 FLUID RECOMMENDATIONS 1-40 LEVEL CHECK 1-40 DRAINS REFILL 1-41 COOLING SYSTEM1-41 FLUID RECOMMENDATIONS 1-41 LEVEL CHECK 1-42 DRAINING S FLUSHING1-42 BRAKE MASTER CYLINDER 1-42 FLUID RECOMMENDATIONS 1-42 LEVEL CHECK 1-42 CLUTCH MASTER CYLINDER1-43 FLUID RECOMMENDATIONS 1-43 LEVEL CHECK 1-43 POWER STEERING PUMP 1-43 FLUID RECOMMENDATION 1-43 LEVEL CHECK1-43 STEERING GEAR 1-43 FLUID RECOMMENDATIONS 1-43 LEVEL CHECK 1-44 CHASSIS GREASING 1-44 BODY LUBRICATION AND MAINTENANCE 1-45 LOCK CYLINDERS 1-45 HOOD LATCH S HINGES 1-45 DOOR HINGES 1-45 BODY DRAIN HOLES1-46 FRONT WHEEL BEARINGS 1-46 TRAILER TOWING 1-46 GENERAL RECOMMENDATIONS 1-46 TRAILER WEIGHT 1-46 HITCH (TONGUE) WEIGHT 1-46 ENGINE 1-47 TRANSMISSION 1-47 HANDLING A TRAILER 1-47 JUMP STARTING A DEAD BATTERY 1-47 JUMP STARTING PRECAUTIONS 1-47 JUMP STARTING PROCEDURE 1-47 SINGLE BATTERY GASOLINE AND DIESEL ENGINE MODELS 1-47 DUAL BATTERY DIESEL MODELS 1-48 JACKING 1-48 JACKING PRECAUTIONS 1-49 MAINTENANCE INTERVALS 1-50 GENERAL RECOMMENDATIONS1-50 BUT THE OWNER'S MANUAL IS DIFFERENT? 1-50 BUT THE REPLACEMENT PART IS DIFFERENT? 1-50 IS MY DRIVING "NORMAL" OR "SEVERE"? 1-50 COMPONENT LOCATIONS UNDERHOOD MAINTENANCE COMPONENT LOCATIONS—R-SERIES 1-11 UNDERHOOD MAINTENANCE COMPONENT LOCATIONS—C-SERIES 1-12 SPECIFICATIONS CHARTS VEHICLE IDENTIFICATION CHART 1-8 GENERAL ENGINE SPECIFICATIONS 1-9 GASOLINE TUNE-UP SPECIFICATIONS 1-31 RECOMMENDED LUBRICANTS 1-36 MAINTENANCE SCHEDULES 1-51 CAPACITIES 1-54 GENERAL HOW TO USE THIS BOOK 1-2 TOOLS AND EQUIPMENT 1-2 SERVICING YOUR VEHICLE SAFELY 1-4 FASTENERS, MEASUREMENTS AND CONVERSIONS 1-5 SERIAL NUMBER IDENTIFICATION 1-7 AND TUNE-UP 1-10 FLUIDS AND LUBRICANTS 1-35 TRAILER TOWING 1-46 iTARTING A DEAD BATTERY 1-47 JACKING 1-48 MAINTENANCE INTERVALS 1-50

1-2 GENERAL INFORMATION AND MAINTENANCE HOW TO USE THIS BOOK This Chilton's Total Car Care manual for 1988-981/2, % and 1 ton Chevrolet and GMC Pick-ups, Blazers, Jimmys, Tahoes, Yukons and Suburbans is intended to help you learn more about the inner workings of your vehicle, while saving you money on its upkeep and operation. The beginning of the book will likely be referred to the most, since that is where you will find information for maintenance and tune-up. The other sections deal with the more complex systems of your vehicle. Systems (from engine through brakes) are covered to the extent that the average do-it-yourselft r can attempt. This book will not explain such things as rebuilding a different! I because the expertise required and the special tools necessary make thi; uneco- nomical. It will, however, give you detailed instructions to help you chan je your own brake pads and shoes, replace spark plugs, and perform many morj jobs that can save you money and help avoid expensive problems. A secondary purpose of this book is a reference for owners who want to understand their vehicle and/or their mechanics better. Where to Begin Before removing any bolts, read through the entire procedure. This will give you the overall view of what tools and supplies will be required. So read, ahead and plan ahead. Each operation should be approached logically and all procedures thoroughly understood before attempting any work. If repair of a component is not considered practical, we tell you how b remove the part and then how to install the new or rebuilt replacement. l(i this way, you at least save labor costs. Avoiding Trouble Many procedures in this book require you to "label and disconnect..." a group of lines, hoses or wires. Don't be think you can remember where (very- thing goes—you won't. If you hook up vacuum or fuel lines incorrectly,! he vehicle may run poorly, if at all. If you hook up electrical wiring incorrec ly, you may instantly learn a very expensive lesson. You don't need to know the proper name for each hose or line. A pied j of masking tape on the hose and a piece on its fitting will allow you to ass jn your own label. As long as you remember your own code, the lines can be rel on- nected by matching your tags. Remember that tape will dissolve in gasaine or solvents; if a part is to be washed or cleaned, use another method of idq itifica- tion. A permanent felt-tipped marker or a metal scribe can be very hand; for marking metal parts. Remove any tape or paper labels after assembly. Maintenance or Repair: Maintenance includes routine inspections, adjustments, and replacertent of parts which show signs of normal wear. Maintenance compensates for wsar or deterioration. Repair implies that something has broken or is not workinji. A need for a repair is often caused by lack of maintenance, for example: dit lining and refilling automatic transmission fluid is maintenance recommended it specific intervals. Failure to do this can shorten the life of the transmission/ transaxle, requiring very expensive repairs. While no maintenance progm.m can prevent items from eventually breaking or wearing out, a general rule is |rue: MAINTENANCE IS CHEAPER THAN REPAIR. TOOLS AND EQUIPMENT I See Figures 1 thru 15 Without the proper tools and equipment it is impossible to properly service your vehicle. It would be virtually impossible to catalog every tool that you would need to perform all of the operations in this book. It would be unwise for the amateur to rush out and buy an expensive set of tools on the theory (hat he/she may need one or more of them at some time. The best approach is to proceed slowly, gathering a good quality set of those tools that are used most frequently. Don't be misled by the low cost of bargain tools. It is far better to spend a little more for better quality. Forged wrenches, 6 or 12-point sockets and fine tooth ratchets are by far preferable to their less expensive counterparts. As any good mechanic can tell yoM, there are few worse experiences than trying to work on a vehicle with bad torjls. Two basic mechanic's rules should be mentioned here. First, whenever the left side of the vehicle or engine is referred to, it means the driver's side. Con- versely, the right side of the vehicle means the passenger's side. Second, screws and bolts are removed by turning counterclockwise, and tightened by turning clockwise unless specifically noted. Safety is always the most important rule. Constantly be aware of the dangers involved in working on an automobile and take the proper precautions. Please refer to the information in this section regarding SERVICING YOUR VEHICLE SAFELY and the SAFETY NOTICE on the acknowledgment page. Avoiding the Most Common Mistakes Pay attention to the instructions provided. There are 3 common mistakes in mechanical work: 1. Incorrect order of assembly, disassembly or adjustment. When taking something apart or putting it together, performing steps in the wrong order usually just costs you extra time; however, it CAN break something. Read the entire procedure before beginning. Perform everything in the order in which the instructions say you should, even if you can't see a reason for it. When you're taking apart something that is very intricate, you might want to draw a picture of how it looks when assembled in order to make sure you get everything back in its proper position. When making adjustments, perform them in the proper order. One adjustment possibly will affect another. 2. Overtorquing (or undertorquing). While it is more common for over- tcrquing to cause damage, undertorquing may allow a fastener to vibrate loose causing serious damage. Especially when dealing with aluminum parts, pay attention to torque specifications and utilize a torque wrench in assembly. If a torque figure is not available, remember that if you are using the right tool to perform the job, you will probably not have to strain yourself to get a fastener tight enough. The pitch of most threads is so slight that the tension you put on the wrench will be multiplied many times in actual force on what you are tightening. There are many commercial products available for ensuring that fasteners won't come loose, even if they are not torqued just right (a very common brand is Loctite"). If you're worried about getting something together tight enough to hold, but loose enough to avoid mechanical damage during assembly, one of trese products might offer substantial insurance. Before choosing a threadlock- irg compound, read the label on the package and make sure the product is compatible with the materials, fluids, etc. involved. 3. Crossthreading. This occurs when a part such as a bolt is screwed into a nut or casting at the wrong angle and forced. Crossthreading is more likely to occur if access is difficult. It helps to clean and lubricate fasteners, then to start threading the bolt, spark plug, etc. with your fingers. I! you encounter resistance, unscrew the part and start over again at a different angle until it can be irserted and turned several times without much effort. Keep in mind that many parts have tapered threads, so that gentle turning will automatically bring the part you're threading to the proper angle. Don't put a wrench on the part until it's been tightened a couple of turns by hand. If you suddenly encounter resistance, and the part has not seated fully, don't force it. Pull it back out to make sure it's clean and threading properly. Be sure to take your time and be patient, and always plan ahead. Allow yourself ample time to perform repairs and maintenance. Your monetary savings will be far outweighed by frustration and mangled knuckles. Begin accumulating those tools that are used most frequently: those associ- ated with routine maintenance and tune-up. In addition to the normal assortment of screwdrivers and pliers, you should have the following tools: • Wrenches/sockets and combination open end/box end wrenches in sizes 1/8- 3/4 in. and/or 3mm-19mm 13/ie in. or % in. spark plug socket (depending on plug type). •"If possible, buy various length socket drive extensions. Universal- joint and wobble extensions can be extremely useful, but be careful when using them, as they can change the amount of torque applied to the socket.

GENERAL INFORMATION AND MAINTENANCE 1-3 • Jackstands (or support. • Oil filter wrench. • Spout or funnel for pouring fluids. • Grease gun for chassis lubrication (unless your vehicle is not equipped with any grease fittings) • Hydrometer for checking the battery (unless equipped with a sealed, maintenance-free battery). • A container for draining oil and other fluids. • Rags for wiping up the inevitable mess. In addition to the above items there are several others that are not absolutely necessary, but handy to have around. These include an equivalent oil absorbent gravel, like cat litter, and the usual supply of lubricants, antifreeze and fluids. This is a basic list for routine maintenance, but only your personal needs and desire can accurately determine your list of tools. After performing a few projects on the vehicle, you'll be amazed at the other tools and non-tools on your workbench. Some useful household items are: a large turkey baster or siphon, empty coffee cans and ice trays (to store parts), a ball of twine, electrical tape for wiring, small rolls of colored tape for tagging lines or hoses, markers and pens, a note pad, golf tees (for plugging vacuum lines), metal coat hangers or a roll of mechanic's wire (to hold things out of the way), dental pick or similar long, pointed probe, a strong magnet, and a small mirror (to see into recesses and under manifolds). A more advanced set of tools, suitable for tune-up work, can be drawn up easily. While the tools are slightly more sophisticated, they need not be outra- geously expensive. There are several inexpensive tach/dwell meters on the mar- ket that are every bit as good for the average mechanic as a professional model. Just be sure that it goes to a least 1200-1500 rpm on the tach scale and-that it works on 4, 6 and 8-cylinder engines. The key to these purchases is to make them with an eye towards adaptability and wide range. A basic list of tune-up tools could include: • Tach/dwell meter. • Spark plug wrench and gapping tool. • Feeler gauges for valve adjustment. • Timing light. , S S«*»8i Fig. 1 All but the most basic procedures will require an assortment of ratchets and sockets Fig. 4 An assortment of pliers, grippers and cutters will be handy for old rusted parts and stripped bolt heads fe"~ i .u '''"^Mlf Fig. 7 Although not always necessary, using specialized brake tools will save time Fig. 2 In addition to ratchets, a good set of wrenches and hex keys will be necessary Fig. 3 A hydraulic floor jack and a set of jackstands are essential for lifting and supporting the vehicle Fig. 5 Various drivers, chisels and prybars are great tools to have in your toolbox TCCS1205 Fig. 6 Many repairs will require the use of a torque wrench to assure the components are properly fastened * Fig. 8 A few inexpensive lubrication tools will make maintenance easier Fig. 9 Various pullers, clamps and separa- tor tools are needed for many larger, more complicated repairs

1-4 GENERAL INFORMATION AND MAINTENANCE Fig. 10 A variety of tools and gauges should be used for spark plug gapping and installation vrr*>fes» ^ Fig. 11 ina ictive type timing light Fig. 13 A vacuum/pressure tester is necessary for many testing procedures r / TCCX1P02 Fig. 12 A screw-in type compression gauge is recommended for compression testing TCCX1POG Fig. 14 M( st modern automotive multi- meters incorporate many helpful features The choice of a timing light should be made carefully. A light which vorks on the DC current supplied by the vehicle's battery is the best choice; it mould have a xenon tube for brightness. On any vehicle with an electronic ignit in system, a timing light with an inductive pickup that clamps around theNo. | spark plug cable is preferred. In addition to these basic tools, there are several other tools and gaut Fig. 15 Proper information is vital, so always have a Chilton Total Car Care manual handy :syou may find useful. These include: • Compression gauge. The screw-in type is slower to use, but e!imii(jates the possibility of a faulty reading due to escaping pressure. • Manifold vacuum gauge. • 12V test light. • A combination volt/ohmmeter • Induction Ammeter. This is used for determining whether or not thdre is current in a wire. These are handy for use if a wire is broken somewhere! n a wiring harness. As a final note, you will probably find a torque wrench necessary for; II but the most basic work. The beam type models are perfectly adequate, althd jgh the SERVICING YOUR VEHICLE SAFELY » See Figures 16,17 and 18 It is virtually impossible to anticipate all of the hazards involved with autt motive maintenance and service, but care and common sense will prevent most accidents. The rules of safety for mechanics range from "don't smoke around gaioline," to "use the proper tool(s) for the job." The trick to avoiding injuries is to develop safe work habits and to take every possible precaution. • Do keep a fire extinguisher and first aid kit handy. • Do wear safety glasses or goggles when cutting, drilling, grinding ing, even if you have 20-20 vision. If you wear glasses for the sake of v wear safety goggles over your regular glasses. or pry- sion, newer click types (breakaway) are easier to use. The click type torque wrenches tend to be more expensive. Also keep in mind that all types of torque wrenches should be periodically checked and/or recalibrated. You will have to decide for yourself which better fits your pocketbook, and purpose. Special Tools Normally, the use of special factory tools is avoided for repair procedures, since these are not readily available for the do-it-yourself mechanic. When it is possible to perform the job with more commonly available tools, it will be pointed out, but occasionally, a special tool was designed to perform a specific function and should be used. Before substituting another tool, you should be convinced that neither your safety nor the performance of the vehicle will be ccmpromised. Special tools can usually be purchased from an automotive parts store or from your dealer. In some cases special tools may be available directly from the tool manufacturer. • Do shield your eyes whenever you work around the battery. Batteries contain sulfuric acid. In case of contact with, flush the area with water or a mixture of water and baking soda, then seek immediate medical attention. • Do use safety stands (jackstands) for any undervehicle service. Jacks are for raising vehicles; jackstands are for making sure the vehicle stays raised until you want it to come down. • Do use adequate ventilation when working with any chemicals or hazardous materials. Like carbon monoxide, the asbestos dust resulting from some brake lining wear can be hazardous in sufficient quantities. • Do disconnect the negative battery cable when working on the electrical system. The secondary ignition system contains EXTREMELY HIGH VOLTAGE. In some cases it can even exceed 50,000 volts. • Do follow manufacturer's-directions whenever working with potentially hazardous materials. Most chemicals and fluids are poisonous.

GENERAL INFORMATION AND MAINTENANCE 1-5 A f*1 ^ TCCS1020 Fig. 16 Screwdrivers should be kept in good condition to prevent injury or damage which could result if the blade slips from the screw Fig. 17 Using the correct size wrench will help prevent the possibility of rounding off a nut Fig. 18 NEVER work under a vehicle unless it is supported using safety stands (jackstands) • Do properly maintain your tools. Loose hammerheads, mushroomed punches and chisels, frayed or poorly grounded electrical cords, excessively worn screwdrivers, spread wrenches (open end), cracked sockets, slipping ratchets, or faulty droplight sockets can cause accidents. • Likewise, keep your tools clean; a greasy wrench can slip off a bolt head, ruining the bolt and often harming your knuckles in the process. • Do use the proper size and type of tool for the job at hand. Do select a wrench or socket that fits the nut or bolt. The wrench or socket should sit straight, not cocked. • Do, when possible, pull on a wrench handle rather than push on it, and adjust your stance to prevent a fall. • Do be sure that adjustable wrenches are tightly closed on the nut or bolt and pulled so that the force is on the side of the fixed jaw. • Do strike squarely with a hammer; avoid glancing blows. • Do set the parking brake and block the drive wheels if the work requires a running engine. Don'ts • Don't run the engine in a garage or anywhere else without proper ventilation—EVER! Carbon monoxide is poisonous; it takes a long time to leave the human body and you can build up a deadly supply of it in your system by simply breathing in a little at a time. You may not realize you are slowly poi- soning yourself. Always use power vents, windows, fans and/or open the garage door. • Don't work around moving parts while wearing loose clothing. Short sleeves are much safer than long, loose sleeves. Hard-toed shoes with neoprene soles protect your toes and give a better grip on slippery surfaces. Watches and jewelry is not safe working around a vehicle. Long hair should be tied back under a hat or cap. • Don't use pockets for toolboxes. A fall or bump can drive a screwdriver deep into your body. Even a rag hanging from your back pocket can wrap around a spinning shaft or fan. • Don't smoke when working around gasoline, cleaning solvent or other flammable material. • Don't smoke when working around the battery. When the battery is being charged, it gives off explosive hydrogen gas. • Don't use gasoline to wash your hands; there are excellent soaps available. Gasoline contains dangerous additives which can enter the body through a cut or through your pores. Gasoline also removes all the natural oils from the skin so that bone dry hands will suck up oil and grease. • Don't service the air conditioning system unless you are equipped with the necessary tools and training. When liquid or compressed gas refrigerant is released to atmospheric pressure it will absorb heat from whatever it contacts. This will chill or freeze anything it touches. • Don't use screwdrivers for anything other than driving screws! A screwdriver used as an prying tool can snap when you least expect it, causing injuries. At the very least, you'll ruin a good screwdriver. • Don't use an emergency jack (that little ratchet, scissors, or pantograph jack supplied with the vehicle) for anything other than changing a flat! These jacks are only intended for emergency use out on the road; they are NOT designed as a maintenance tool. If you are serious about maintaining your vehicle yourself, invest in a hydraulic floor jack of at least a 11/2 ton capacity, and at least two sturdy jackstands. FASTENERS, MEASUREMENTS AND CONVERSIONS Bolts, Nuts and Other Threaded Retainers » See Figures 19 and 20 Although there are a great variety of fasteners found in the modern car or truck, the most commonly used retainer is the threaded fastener (nuts, bolts, screws, studs, etc.). Most threaded retainers may be reused, provided that they are not damaged in use or during the repair. Some retainers (such as stretch bolts or torque prevailing nuts) are designed to deform when tightened or in use and should not be reinstalled. Whenever possible, we will note any special retainers which should be replaced during a procedure. But you should always inspect the condition of a retainer when it is removed and replace any that show signs of damage. Check all threads for rust or corrosion which can increase the torque necessary to achieve the desired clamp load for which that fastener was originally selected. Additionally, be sure that the driver surface of the fastener has not been com- promised by rounding or other damage. In some cases a driver surface may become only partially rounded, allowing the driver to catch in only one direc- tion. In many of these occurrences, a fastener may be installed and tightened, but the driver would not be able to grip and loosen the fastener again. If you must replace a fastener, whether due to design or damage, you must ALWAYS be sure to use the proper replacement. In all cases, a retainer of the LOCKWASHERS CO) •HI • TCCS1036 Fig. 19 There are many different types of threaded retainers found on vehicles

1-6 GENERAL INFORMATION AND MAINTENANCE h-c —i 1 i F ^^HI i r (. A — ' ] A - Length k J B - Diameter (major diameter) >yx^ C - Threads per inch or mm E - Size of the wrench required r— E —«1 F - Root diameter (minor diameter) TCCS1038 Fig. 20 Threaded retainer sizes are determined using these me surements - ^ r^=====^^$A=sf~ —1 '! Z i DEFLECTING BEAM —-S—-*~~—?^^r~~ & o , fe'JH--' ' (n ] o s'.1,1,1,' 't\ i 1 CLICK TYPE TCCS1015 Fig. 21 Various styles of torque wrenches are usually available at your local automotive supply store same design, material and strength should be used. Markings on the he|ds of most bolts will help determine the proper strength of the fastener. The saj ne material, thread and pitch must be selected to assure proper installation nd safe operation of the vehicle afterwards. Thread gauges are available to help measure a bolt or stud's thread. l|ost automotive and hardware stores keep gauges available to help you selec the proper size. In a pinch, you can use another nut or bolt for a thread gauc;. If the bolt you are replacing is not too badly damaged, you can select a match iy finding another bolt which will thread in its place. If you find a nut which threads properly onto the damaged bolt, then use that nut to help select he replacement bolt. ••-••' WARNING Be aware that when you find a bolt with damaged threads, you may also find the nut or drilled hole it was threaded into has also teen damaged. If this is the case, you may have to drill and tap thd hole, replace the nut or otherwise repair the threads. NEVER try to I irce a replacement bolt to fit into the damaged threads. Torque Torque is defined as the measurement of resistance to turning or rotat ig. tends to twist a body about an axis of rotation. A common example of thi would be tightening a threaded retainer such as a nut, bolt or screw. Mee ;uring torque is one of the most common ways to help assure that a threaded retainer has been properly fastened. When tightening a threaded fastener, torque is applied in three distinc areas, the head, the bearing surface and the clamp load. About 50 percent of thi mea- sured torque is used in overcoming bearing friction. This is the friction b tween the bearing surface of the bolt head, screw head or nut face and the base nater- ial or washer (the surface on which the fastener is rotating). Approximate 140 percent of the applied torque is used in overcoming thread friction. This laves only about 10 percent of the applied torque to develop a useful clamp IDE i (the force which holds a joint together). This means that friction can account 'pr as much as 90 percent of the applied torque on a fastener. TORQUE WRENCHES I See Figure 21 In most applications, a torque wrench can be used to assure proper installation of a fastener. Torque wrenches come in various designs and most auDmo- tive supply stores will carry a variety to suit your needs. A torque wrench should be used any time we supply a specific torque value for a fastener. Again, the general rule of "if you are using the right tool for the job, you should not have to strain to tighten a fastener" applies here. Beam Type The beam type torque wrench is one of the most popular types. It cons sts of a pointer attached to the head that runs the length of the flexible beam (srpft) to a scale located near the handle. As the wrench is pulled, the beam bends fnd the pointer indicates the torque using the scale. Click (Breakaway) Type Another popular design of torque wrench is the click type. To use the click type wrench you pre-adjust it to a torque setting. Once the torque is reached, the wrench has a reflex signaling feature that causes a momentary breakaway of the torque wrench body, sending an impulse to the operator's hand. Pivot Head Type I SeeFigure 22 Some torque wrenches (usually of the click type) may be equipped with a pivot head which can allow it to be used in areas of limited access. BUT, it must be used properly. To hold a pivot head wrench, grasp the handle lightly, and as you pull on the handle, it should be floated on the pivot point. If the handle comes in contact with the yoke extension during the process of pulling, there is a very good chance the torque readings will be inaccurate because this could alter the wrench loading point. The design of the handle is usually such as to make it inconvenient to deliberately misuse the wrench. ••It should be mentioned that the use of any U-joint, wobble or extension will have an effect on the torque readings, no matter what type of wrench you are using. For the most accurate readings, install the socket directly on the wrench driver. If necessary, straight extensions (which hold a socket directly under the wrench driver) will have the least effect on the torque reading. Avoid any extension that alters the length of the wrench from the handle to the head/driving point (such as a crow's foot). U-joint or wobble extensions can greatly affect the readings; avoid their use at all times. PIVOTED HANDLE TORQUE WRENCH TCCS1041 Fig. 22 Torque wrenches with pivoting heads must be grasped and used properly to prevent an incorrect reading Rigid Case (Direct Reading) A rigid case or direct reading torque wrench is equipped with a dial indicator to show torque values. One advantage of these wrenches is that they can be held at any position on the wrench without affecting accuracy. These wrenches are often preferred because they tend to be compact, easy to read and have a great degree of accuracy.

1998 GMC Sierra Pickup 2500 Repair Manual

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