Century V6-231 3.8L (1985)
Shift Modulator: All Technical Service Bulletins
A/T - Repeat Transaxle Failure, Vacuum Lines
Bulletin:
85-7440-10
Date:
Oct 1985
Ref. No.: 85-260-7440
SUBJECT:
PINCHED OR KINKED MODULATOR VACUUM LINES AND DELETION OF ASPIRATOR/SOLENOID SYSTEM
MODELS AFFECTED:
1984-85 CENTURYS AND ELECTRAS EQUIPPED WITH 3.8L (VIN CODE 3) V-6 ENGINES AND THM 440-T4
TRANSAXLES
A repeat THM 440-T4 transaxle failure may be due to pinched or kinked vacuum lines causing low oil pressure. Visual inspection of lines is inadequate
to detect this condition. To diagnose this condition connect a vacuum gage at the vacuum modulator by use of a tee with adequate hose length to observe
the gage. With engine running and throttle closed vacuum at modulator should be 13-17 in.hg. When this throttle is opened, vacuum drop should be
IMMEDIATE. A slow vacuum drop when this throttle is opened indicates a kinked or pinched vacuum line.. Vacuum retained in the modulator will
reduce line pressure and may result in second clutch distress.
VACUUM HARNESS ASM (ENG ASM)
In mid January the aspirator/solenoid was eliminated and replaced with a solid steel line to supply vacuum to the modulator. See illustration. If a
condition of inadequate vacuum supply to the modulator exists or if the aspirator solenoid should fail or you are experiencing second gear starts or
excessively firm shifts, it is recommended that a solid steel line minus the aspirator be installed as shown in the illustration.
Also whenever an exchange unit or a remanufactured transmission is installed in one of these vehicles that still has the aspirator system on it, it should be
removed and the new steel line installed.
The electrical connector to the aspirator system solenoid should be taped back out of the way.
A formed steel line, two pieces of 7/32 vacuum hose and new emission label are available from GMWDD under the following part numbers.
MODEL
PART NUMBER
Century
25527722
