A/T - No Upshift/Governor Contamination

TSB 88-16 (Mar)

SUBJECT: GM TRANSMISSIONS

PROBLEM: No upshift

CAUSE:
May be caused by imprex material lodged in a seat or under a ball in the governor. Imprex material is used to seal transaxle cases against porosity and has the appearance of RTV sealer. This material can prevent the governor balls from seating properly, or can plug the feed passage and result in low governor pressure.

CURE:
If it is suspected that imprex material has migrated into the governor, remove the governor from the transaxle. Reinstall the 9overnor cover without the governor. Start the engine and shift transaxle to drive for approximately 5 minutes. This will flush out the governor oil passages.

Clean the governor and check for proper seating of the governor balls. Hold the weights outward against the bails and pour solvent into the governor shaft. If solvent leaks past the balls, replace the governor. If no leakage is found, reinstall the governor and verify operation.

If the above actions do not correct the no-upshift condition on the THM 440-T4, check these three areas for causes of low governor pressure:

1. Governor pipe retainer bolt loose, or missing
2. Governor pipe retainer gasket missing, or mislocated.




3. Plugged governor feed pipe screen (See Figure 1)