A/T - Diagnosis & Unit Repair Service Manual Update
Group Ref.: TransmissionBulletin No.: 377149A
Date: April 1994
SERVICE MANUAL UPDATE
Subject:
SECTION 7A - TRANSMISSION DIAGNOSIS AND
SECTION 7B - TRANSMISSION UNIT REPAIR
Models:
1994 CHEVROLET AND GMC TRUCK C/K, P TRUCKS, AND G VANS
TRANSMISSION APPLICATIONS:
1994 HYDRA-MATIC 4L80-E/4L80-EHD (MT1)
THIS BULLETIN IS BEING REVISED TO CORRECT A UNIT REPAIR MANUAL PAGE REFERENCE, AND TO ADD A FIGURE THAT WAS OMITTED FROM THE FIRST PUBLICATION. PLEASE DISCARD CORPORATE BULLETIN # 377149 940101.
SERVICE INFORMATION:
Diagnosis
Page 7A-17A-21 through 7A-17A-24, Malfunction Code Diagnosis and Default Charts;
Specific engine designators changed in codes 21, 22, and 74, Column heading "Probable Cause" changed to "Code Setting Criteria",
Corrections made to the Code Setting Criteria for codes 39, 53, 58, 73, 75, and 85;
Corrections made to the Default Action Column for codes 39, 52, 53, 58, 68, 72, 73, 75, 86 and 87;
The word "inhibit" is changed to "no" in codes 21, 22, 28, 52, 53, 68, 71, 74, 75, 81 and 83;
"Soft Landing" is defined in code 75; and, Symbols are changed to words in codes 28, 37 and 38.
Page 7A-17A-57, 4L80-E/4L80-EHD Wiring Diagram
Wire colors updated and transmission component terminal designators corrected.
Page 7A-17A-58, 4L80-E/4L80-EHD Component Resistance Chart
Wire colors updated.
Page 7A-17-59, 4L80-E Transmission Pressure Switch Assembly Resistance Check
Added "Turn Engine Off", corrected reference for intermittent condition and high/low resistance definition below chart.
Unit Repair
Pages 7A-17B-36 and 7A-17B-37, Pump Assembly
Step # 3; Pressure regulator (231) and Boost Valve Assembly (228) designators corrected. Illustration updated to show the Valve Bore Plug (232) for the Pressure Regulator (231) and the Boost Valve Assembly (228) changed to the same plug as the TCC Valve (233).
Page 7A-17B-38, Figure 71, Measuring Pump Body Face to Gear Clearance
Pump Driven Gear (204) and Pump Drive Gear (205) designators corrected on illustration.
Page 7A-17B-39, Figure 73, Assembling Pump Body and Pump Cover.
Pump body and cover alignment band tool designation (J 21368) added to Illustration.
Page 7A-17B-52, Figure 98, Installing Fourth Clutch Snap Ring and Figure 99, Installing Gasket. Pump Cover to Case
Corrected illustrations to match titles.
SERVICE MANUAL REFERENCE:
Please insert the following pages into your 1994 Service Manual, 4L80-E Automatic Transmission Diagnosis and 4L80-E Automatic Transmission Unit Repair Sections.
Page 7A-17A-21
Page 7A-17A-22
Page 7A-17A-23
Page 7A-17A-24
Page 7A-17A-57
Page 7A-17A-58
Page 7A-17A-59
Page 7A-17B-36
Page 7A-17B-37
Page 7A-17B-38
Page 7A-17B-39
Page 7A-17B-52