A/T - Service Transmission Replacement
BULLETIN NUMBER: 92-7A-154SECTION: 7A
NUMBER: 6
CORPORATE REFERENCE NUMBER: 377114R
DATE: April 1993
SUBJECT:
SERVICE PROCEDURE POLICY CHANGES
MODELS:
1991-92 C/K, R/V, AND P TRUCKS AND G VANS WITH 4L80-E/4L80-EHD TRANSMISSIONS
This bulletin covers changes to the HYDRA-MATIC 4L80-E/4L80-EHD Service Policy for in warranty vehicles. This bulletin does not apply to out of warranty vehicles. The only service options available will be as listed below. SRTA models and service parts can be ordered from your local General Motors Service Parts Operations (GMSPO) Parts Distribution Center. New Service Policy Permits On-Car Service or SRTA Only. ONLY limited on-car repairs or SRTA will be the service options available for vehicles currently covered under the warranty period.
Conditions when SRTA usage is appropriate: Any repairs that cannot be completed by replacement of the parts shown in Figure 1.
Dealer HYDRA-MATIC 4L80-E transmission repairs include: Limited on-vehicle serviceable items. Reference Figure 1. Parts needed to perform limited on-vehicle service on a HYDRA-MATIC 4L80-E transmission are available through your local Parts Distribution Center (PDC).
IMPORTANT:
Do not attempt repairs on a 1991 or 1992 HYDRA-MATIC 4L80-E, unless the part is shown in Figure 1 and listed in the repair parts list in this bulletin. All returned HYDRA-MATIC 4L80-E transmissions will be disassembled and inspected in an effort to increase product integrity. Attempting repairs could destroy root cause analysis data.
The Rear Internal Gear Campaign Bulletin 92-C-17 dated July 1992 will not be affected by this bulletin. Continue to implement this campaign. An SRTA should NOT be used to complete this campaign. This is the only exception.
COOLER FLUSHING
Cooler flushing and a flow check MUST be performed whenever a transmission is removed for service. It is essential to flush the cooler prior to a SRTA installation, or when fluid contamination is suspected. Use Kent-Moore tool J35944 and solvent J35944-20 to flush the cooler. Instructions are published in each Service Manual On-vehicle Service Section.
SERVICE PARTS INFORMATION
HYDRA-MATIC 4L80-E/4L80-EHD SRTA Model Replacement Chart
1991-1992 HYDRA-MATIC 4L80-E/4L80-EHD On-vehicle Serviceable Components:
HYDRA-MATIC 4L80-E/4L80-EHD QUICK CHECK PROCEDURE
1. Write down customer complaint.
2. Check fluid level and condition:
^ Burned? Remember brown color of the fluid may be OK. Refer to Service Manual.
^ Low or overfilled? Correct as necessary.
3. Use the TECH 1 to check for stored Diagnostic Trouble Codes (DTC).
^ Remember, Code 12 tells you that the diagnostic function of PCM is functioning correctly.
^ If there is a stored transmission code other than Code 12, refer to Service Manual for diagnostic procedures.
4. Clear codes, test drive truck. Monitor powertrain with a TECH 1. For shift points refer to the shift speed chart.
5. Recheck for stored codes. Correct all codes before continuing.
6. If transmission operates properly-stop.
7. For a harsh or soft shift condition confirm correct cal prom, then perform transmission line pressure check procedure. If line pressure is too high or too low, replace the transmission.
8. For a poor performance condition verify engine performance, then refer to torque converter evaluation in Service Manual.
9. For a vibration or noise condition refer to torque converter vibration test procedure in Service Manual.
10. If all the steps check out ok and the transmission still does not function correctly, refer to Service Manual for diagnosis information. If the diagnosis information determines that an internal component of the transmission needs to be serviced, then replace the transmission. Do not disassemble the transmission.