A/T - 440T4 Poor Shift Quality

SIL: 86-1 (Feb)

SUBJECT: 440 T4

PROBLEM:
Poor Shift Quality Hard, Soft, Slipping, or Inconsistent Shifts

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 gauge at the vacuum modulator by use of a tee with adequate hose length to observe the gauge. With the 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.




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