A/T - 700R4 Loss Of Wide Open Throttle 3-4 Upshift
BULLETIN NO.: 9174L60-08CORP. REF. NO.: 077155
DATE: Jan., 1991
TRANSMISSION APPLICATIONS:
1989-1991 HYDRA-MATIC 4L60 (MD8)
SUBJECT:
Loss of Wide Open Throttle 3-4 Upshift When Hot/Tuliped Intake Valves (Update Transmission Calibration and Replace Engine Thermostat)
TRANSMISSION MODELS: 9YNM, 0BPM, 1BFM
VEHICLE APPLICATIONS: B-Car (5.7L Police Only)
THIS BULLETIN CANCELS AND REPLACES BULLETIN 897700-05 (CORP REF. # 977133, CHEVROLET BULLETIN 89-226-7A, GM OF CANADA BULLETIN 89-7700107)
BULLETIN COVERS:
Service and parts information for some 1989-91 Police vehicles (5.7L "B" car). These vehicles may experience a loss of wide open throttle 3-4 upshift when hot. This can cause tuliped intake valves during extended high speed operation in third gear. An updated transmission calibration has been released to address this condition. A new engine thermostat was previously released, and should be used in conjunction with the new transmission calibration.
Drivers of Police vehicles should note that during high speed pursuit, the shift selector should be in OD (Overdrive). This maximizes powertrain performance and lessens problems that may occur during extended high engine speeds.
SERVICE INFORMATION:
The transmission service package in this bulletin may be used to service the following models of the HYDRA-MATIC 4L60:
9YNM, 0BPM, 1BFM
If service is necessary on the 1BFM model, you may not have to replace the TV boost valve and bushing. If the transmission Julian date is 267 (September 24) or later, the transmission already contains the updated TV boost valve and bushing.
Refer to Chevrolet Service Bulletin 90-215-6B for previously available information on a new engine thermostat.
Loss of Wide Open Throttle 3-4 Upshift When Hot/Tuliped Intake' Valves (Update Transmission Calibration and Replace Engine Thermostat)
DATE OF PRODUCTION CHANGE: (Figure 1)
Beginning October 19, 1990 (Julian Date 292), the 1BFM model of the HYDRA-MATIC 4L60 was replaced by the 1BJM model. The 1BJM contains the updated transmission calibration.
Beginning Start of Production 91, all Police models of the Chevrolet Caprice were built with the new engine thermostat.
SERVICE PROCEDURE: (Figure 2)
Install the TV boost valve and spring into the pump cover assembly. Install the 3-4 throttle valve, bushing and spring into the control valve assembly. Follow the procedures listed in the Automatic Transmission Unit Repair Section of the applicable Service Manual.
IMPORTANT
Do not install a 1991 model transmission into a 1989 or 1990 vehicle. Part changes made in the 1991 model year make the 1991 models incompatible with earlier vehicle systems.
SERVICE PARTS INFORMATION:
DESCRIPTION PART NUMBER
Police Package 8673948
(Includes: TV boost valve and
bushing, 3-4 throttle valve,
bushing and spring)
Parts are expected to be available on December 17, 1990. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.