Article 2094 - Automatic Transmission - Non-Adjustable Vacuum Diaphragm

TSB #132 - January 30, 1970
(All 1970 Vehicles with C4 and C6 Automatic Transmissions)

There will be approximately 90,000 C6 and 10,000 C4 automatic transmissions built using a special design non-adjustable vacuum diaphragm assembly identified with a while stripe. To accommodate this design three different length throttle control valve rods; the standard production rod, 1.67 inches long with no identification; one 1.64 inches long, identified by a blue paint daub; and one 1.00 inch long, identified by a daub of yellow paint; are used to obtain correct pressures.

Use of the special non-adjustable diaphragm will not affect the transmission function or shift points in any way, and therefore, should not be replaced unless there is a failure of the diaphragm. If the non-adjustable diaphragm assembly needs replacing, the pre-adjusted service diaphragm assembly, C4AZ-7A377-B, should be installed.

When replacing a non-adjustable diaphragm in service, it must be determined which rod is installed.
    1. If the original diaphragm rod is not color coded, replace the vacuum diaphragm only.
    2. If the original diaphragm rod is color coded, either:
      a. Install diaphragm rod C4AZ-7A380-A with the service replacement diaphragm assembly, or
      b. Install gauges and adjust the replacement diaphragm assembly to obtain the correct pressure specifications. (Refer to 1970 Shop Manual, Page 17-01-09, Vacuum Diaphragm Adjustment, Non-Altitude Compensating Type.)

Part NumberNameClassAvail.
C4AZ-7A377-BDiaphragm Assy. - Vacuum Throttle ValveAOK
C4AZ-7A380-ARod - Throttle Control ValveAOK

PRODUCTION CHANGE: October 9, 1969
WARRANTY STATUS: Reimbursable under provisions of Warranty & Policy Manual.
Operation: 7-7377-A - Replace (0.3 Hr.)
7-7377-B - Adjust (0.5 Hr.)
See page 7A7 of the Service Labor Time Standards for codes.

NOTE: This TSB article has been superseded by Article 2195, TSB #135 - Automatic Transmission Non-Adjustable Vacuum Diaphragm, dated March 13, 1970.