4L80E 4L80 Transmission Gearbox REBUILD PROCEDURE Manual

GM 4L80E Rebuild Procedures Written by Clifford McCormick

©2003 ATRA. All Rights Reserved. Printed in U. S. A. iii 4L80E Rebuild Procedures Program Introduction… The General Motors 4L80E, in production since 1991, has become the workhorse of GM’s light truck series. This unit has also surfaced in some rather exotic and unexpected vehicles simply because those manufacturers wanted one of the best, most reliable units available at the time. Based on the bulletproof THM 400, which could take just about anything a car or truck could dish out without breaking a sweat, the 4L80E was the natural evolution of the 400, updating the design with a beefy overdrive section built into the case in front of the venerable tried-and-true three speed. No longer does the old governor/modulator debate tell the transmission what to do, when and how much to do it. Fully computerized control of the shift points, torque converter clutch engagement and line pressure control ensure that the 4L80E will be with us for quite some time to come, easily interfacing with the newest powertrain control and diagnostic computer systems. There may be parts of the rebuild process that you are not very familiar with, or you may be new to this particular type of transmission. In either case, you need some point of reference- something that will show you how to proceed when you are not sure (or have no idea whatsoever), and that is exactly what this book is designed to do. You will not find a photocopied section out of a factory manual between these covers. In fact, you will notice a substantial difference between the book you are holding and any other books written on the subject. This is because, as this book was being written, the author was rebuilding a 4L80E step by step as he was writing this book. This helps assure that there would be no missing steps (and it was also quite handy for taking pictures along the way…). This book was written for transmission rebuilders by a transmission rebuilder, in plain English rather than complex ‘factoreze’ terminology, or instructions that have been partially ‘transrated’ from some other language. So, whether you’ve already done a few of the 4L80E units or are about to tackle your first one, this book will show you how to get through the sticky parts of a rebuild, as well as the most thorough way to get through the job, start to finish. Thank you for your attention, your efforts and your trust.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. v 4L80E Rebuild Procedures Table Of Contents Unit Disassembly Pump Fourth Clutch Assembly Overrun clutch/OD Planet Forward Clutch Drum Direct Clutch Drum Geartrain Case Preparation Valve Body Unit Assembly Page 1 Page 12 Page 23 Page 28 Page 36 Page 42 Page 49 Page 61 Page 65 Page 74 This program has been designed by the Automatic Transmission Rebuilders Association (ATRA) to be used by qualified automotive transmission technicians. Since the circumstance of its use is beyond ATRA’s control, ATRA assumes no liability for the use of such information or any damages incurred through its use and application. Nothing contained in this program is to be considered contractual or providing some form of warranty on the part of ATRA. No part of this program should be construed as recommending any procedure which is contrary to the vehicle manufacturer’s procedures. ATRA recommends that only certified automotive technicians with experience in transmission diagnosis and repair perform the procedures in this program. This program contains copyrighted material belonging to ATRA. No part of this program may be reproduced or used in any form by any means- graphic, electronic or mechanical, including photocopying, recording, electronic, or information storage-and-retrieval systems- without the express written permission from ATRA. ATRA® and the ATRA® logo are registered trademarks of the Automatic Transmission Rebuilders Association. Public exhibition or use of this material for group training or as part of a school curriculum, without the express written permission of ATRA, is prohibited by law. For information on using this material for independent training programs, contact ATRA at (805) 604- 2000. ©2003 ATRA. All rights reserved. Printed in U.S.A.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. 1 4L80E Rebuild Procedures Unit Disassembly Step 1: Unbolt the shift lever and speed sensors, remove them from the case, then use a pick to remove the o-rings from the sensors. Note: The next two steps only apply to 2-wheel drive units. Step 2: The rear seal usually needs to get repeatedly bashed with a hammer and screwdriver or chisel to remove it from the extension housing as shown. This will definitely be easier to do while the housing is still bolted to a big, heavy transmission, rather than chasing the extension housing with your tools all over your bench and the shop floor after it’s been removed from the unit. Save yourself the embarrassment of somebody else seeing this clown act by removing the seal now in a dignified manner.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. 2 4L80E Rebuild Procedures Step 3: Remove the extension housing bolts, and slide the extension housing off of the case. Remove the o-ring from the shaft groove, paying careful attention to any thrust washers, bearings or seals on the shaft; the exact configuration depends on the unit you're working on. Step 4: Unbolt the transmission oil pan, and remove the pan, gasket and oil filter from the unit. Be careful with the pan gasket if it’s rubber and has metal bolt holes— it's reusable as long as it’s still soft and isn’t nicked or cut anywhere. Discard the filter. Step 5: Carefully disconnect the transmission wiring harness connectors from the solenoids and switches on the valve body.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. 3 4L80E Rebuild Procedures Step 6: Push a 1-1/4", 12-point socket or box wrench over the transmission case connector to compress the retaining clips, and carefully push the case connector into the case to remove it. Don't pull on the wires; they can break internally, and cause electrical problems later.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. 4 4L80E Rebuild Procedures Step 7: Remove the Pressure Switch Manifold (PSM) bolts, and remove the switch. Step 8: Remove the bracket holding the lube oil pipe in place, and carefully remove the pipe from the unit. Step 9: Unbolt the valve body and accumulator assembly. Remove the valve body and accumulator assembly, separator plate and gaskets from the transmission.

©2003 ATRA. All Rights Reserved. Printed in U. S. A. 5 4L80E Rebuild Procedures Step 10: Remove the case filter and checkballs from the case. Step 11: Remove the Manual 2 brake band servo and spring, located directly in front of the low/reverse servo cover. Step 12: Unbolt the low/reverse servo cover. Remove the cover, gasket, servo and return spring from the case. Discard the gasket.

4L80E 4L80 Transmission Gearbox REBUILD PROCEDURE Manual

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