SMU - SEC. 7A - TRANSMISSION UNIT REPAIR UPDATE 3-4 CLUTCH

Subject: SERVICE MANUAL UPDATE - SECTION 7A - TRANSMISSION UNIT REPAIR UPDATE 3-4 CLUTCH Models Affected: 1987-93 FIREBIRD MODELS

TRANSMISSION APPLICATIONS: 1987-93 HYDRA-MATIC 4L60 (MD8)

TRANSMISSION MODELS: ALL

BULLETIN COVERS:

New Product Information for 1993 HYDRA-MATIC 4L60 transmissions. This information has been updated since publication of the 1993 Service Manual and should be noted accordingly. Be certain to familiarize yourself with these updates to properly repair the 1993 HYDRA-MATIC 4L60 transmissions.

DATE OF PRODUCTION CHANGE:

On January 05, 1993 (Julian Date 005) HYDRA-MATIC 4L60 transmissions were built with an improved design 3-4 clutch. The improved design consisted of combining the 3rd and 4th clutch ring retainer plate (Ill. 652), the 3rd and 4th clutch apply (stepped) plate (Ill. 653) and the 3rd and 4th clutch (steel) plate (Ill. 654C) into one 3rd and 4th clutch apply plate (Ill. 653) Figure 1. The 3rd and 4th clutch steel plates are also thicker and the backing plate selection has changed as noted in Figure 2.

NOTE: In the overhaul repair kits for the HYDRA-MATIC 4L60 there are two (2) sets of 3rd and 4th clutch fiber plates. The two 3rd and 4th clutch fiber plates are calibration sensitive and interchanging the wrong plates may cause premature failure. The following chart shows which models should use the plates labeled 11205011 Figure 3.

1991 1992 1993

1AAM 2ADM 3AAM 3ADM 1APM 2AKM 3AFM 3ASM 1CNM 2BFM 3BAM 3BBM 1CYM 2CHM 3BCM 3BFM 1FYM 2CJM 3BHM 3BRM 1KWM 2FUM 3BWM 3CPM 1LHM 2KJM 3FAM 3FDM 1RCM 2LHM 3FFM 3FMM 1RDM 2WCM 3LHM 3SFM lYHM 2YCM 3YAM 3YCM 2YDM 3YDM

ILL DESCRIPTION NO.

600 SPRING ASM., 3-4 CLUTCH BOOST (5) 615 BEARING ASSEMBLY, STATOR SHAFT/SELECTIVE WASHER 616 WASHER, THRUST (SELECTIVE) 617 RETAINER AND BALL ASM., CHECK VALVE 620 RETAINER AND CHECKBALL ASSEMBLY 621 HOUSING AND SHAFT ASSEMBLY, INPUT 623 PISTON, 3RD AND 4TH CLUTCH 625 RING, 3RD AND 4TH CLUTCH (APPLY) 626 SPRING ASSEMBLY, 3RD AND 4TH CLUTCH 627 RETAINER AND BALL ASSEMBLY, FORWARD CLUTCH HOUSING 628 HOUSING, FORWARD CLUTCH 630 PISTON, FORWARD CLUTCH 632 PISTON, OVERRUN CLUTCH 633 BALL, OVERRUN CLUTCH 634 SPRING ASSEMBLY, OVERRUN CLUTCH 635 SNAP RING, OVERRUN CLUTCH SPRING RETAINER 636 SEAL, INPUT HOUSING TO OUTPUT SHAFT 645A PLATE ASSEMBLY, OVERRUN CLUTCH (STEEL) 645B PLATE, OVERRUN CLUTCH (FIBER)

A FORWARD CLUTCH SPRAG ASSEMBLY 637 BEARING ASSEMBLY, INPUT SUN GEAR 638 SNAP RING, OVERRUN CL. HUB RETAINING 639 HUB, OVERRUN CLUTCH 641 RETAINER AND RACE ASSEMBLY, SPRAG 642 FORWARD SPRAG ASSEMBLY 643 RETAINER RINGS, SPRAG ASSEMBLY 644 RACE, FORWARD CLUTCH (OUTER) 646 PLATE, FORWARD CLUTCH (APPLY) 648 PLATE, FORWARD CLUTCH (WAVED) 649A PLATE ASSEMBLY, FORWARD CLUTCH (STEEL) 649B PLATE, FORWARD CLUTCH (FIBER) 650 PLATE, FORWARD CLUTCH CLUTCH BACKING (SEL.) 651 RING, FORWARD CLUTCH BACKING PLATE RETAINER 653 PLATE, 3RD AND 4TH CLUTCH APPLY (STEPPED) 654A PLATE ASSEMBLY, 3RD AND 4TH CLUTCH (FIBER) 654B PLATE, 3RD AND 4TH CLUTCH (STEEL) 655 PLATE, 3RD AND 4TH CLUTCH BACKING (SEL.) 656 RING, 3RD AND 4TH CLUTCH BACKING PLATE RETAINER 698 PLUG, ORIFICED CUP

Figure 56 Input Clutch Assembly

Inspect Figures 57 and 59 o Turbine shaft 0-ring seal (618) for: - Damage. - Nicks or cuts. o Input housing check valve ball (620): - The ball must move freely. - Leak check the ball with solvent. Important

o If the 3-4 clutch plates are bumed or worn and a cause is not found during diagnosis or disassembly, replacement of the retainer and check ball assembly may be required (Figure 57).

E3 Remove or Disconnect

Figure 60

o Tap out retainer and ball assembly.

E3 Install or Connect

Figures 58 and 60

o Using same tools, tap in retainer and ball assembly until shoulder is seated in housing.

o The 3-4 clutch apply plate (653) for: - Flatness. - Bent tangs. - Surface finish damage.

Assemble

Figures 72 through 75

1. Forward clutch apply plate (646) into the input clutch housing. o Index as shown.

2. Waved steel forward clutch plate (648) into the input clutch housing. o Index as shown.

3. The remaining forward clutch plates (649) into the input clutch housing.

o Start with a steel plate and alternate with composition.

4. Forward clutch selective backing plate (650).

5. Forward clutch retaining ring (651).

Forward Clutch Piston Travel Check

Figure 75 Measure 1. With the overrun clutch and forward clutch fully assembled in the Input Housing, check the end clearance between the backing plate (650) and the retaining ring (65 1) with two feeler gages. 2. Proper forward clutch backing plate travel should be 0.75 to 1.60 mm (0.030 to 0.063 inch). 3. Select the proper backing plate from the chart to obtain the correct clearance.

3-4 Clutch Piston Travel Check

Figure 77 Measure o Check the end clearance between the backing plate (655) and the first composition plate with a feeler gage. o Select the proper backing plate from the chart to obtain the correct clearance for model you are working on.

Clutch Air Check

Figure 78 Air check the 3-4, forward, and overrun clutches by applying air pressure at the feed holes in the turbine shaft. (When the overrun clutch is checked, the air will blow by the forward clutch piston lip seals and exit out the forward clutch feed hole in the turbine shaft.)

3-4 Clutch Assembly Figures 76 and 80

Assemble

1. The 3-4 clutch apply plate (653). o Index each leg into the apply ring legs. 2. The 3-4 clutch plates (654). o Start with steel and alternate with composition as shown in (Figure 80). o First steel plate has the same spline configuration as apply plate. 3. The 3-4 boost springs (600). 4. The 3-4 clutch backing plate (655) and retainer ring (656). o Chamfered side up.

Turbine Shaft Seals

Figure 79 Tools Required: J 36418-1 Seal Installer J 364l8-2A Seal Sizer

Assemble 1. Install four turbine shaft oil seal rings (619) using J-36418-1. Adjust o Adjust screw to obtain proper height. 2. Use J 36418-2A to size the seals after installation.

Reverse Input Clutch Assembly Figures 81 through 86 Tools Required: J 23327-1 Clutch Spring Compressor J 25018-A Clutch Spring Compressor Adaptor Disassemble Figures 81 and 82 1. Retaining ring (614) from reverse input housing. 2. Backing plate (613). 3. Clutch plates (612) and Belleville steel plate (611). 4. Install J 23327-1 and J 25018-A. o Compress the spring assembly. 5. Spring assembly retainer ring (610) and spring assembly (609). 6. Reverse input clutch piston (607). o Inner and outer lip seals (608).

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.