PowerTrain Pro: Automatic Transmission

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Friday, November 1, 2013 - 07:00
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After overhaul the vehicle loses both forward and reverse movement. When the Service Fast Learn (SFL) procedure was attempted to reset the shift adapts, it would abort approximately half way through the process.

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Cause # 1:
When the transmission was disassembled the 1-2-3-4 clutch pack retaining snap ring was found to have popped out of the clutch drum snap ring groove.

The 1-2-3-4 clutch drum has one machined lug that is different from all the others. If any part of the solid area of the snap ring is positioned against this lug, it will not be fully seated and will pop out of place during the initial road test.

Cause # 2:
When the transmission was disassembled, the input carrier was found to be installed upside down onto the 1-2-3-4/3-5 Reverse Housing. This prevented the 1-2-3-4 clutch drum splines from engaging the input carrier. Notice in Figure 5 that the splines on the input carrier and the mating splines in the drum are short. The input carrier will drop over the sun gear and rotate in place which would make it appear normal.

Cause # 3:
When a new 3-5-Reverse clutch drum is replaced, it is installed without the 3-5 -Reverse clutch drum bearing. A new drum does not come with this bearing unless the 3-5-Reverse clutch drum kit is purchased.

# 1. Install the clutch pack retaining snap ring so the snap ring gap straddles the machined lug in the drum.

# 2. Make certain the splines of the input carrier engage the splines of the 1-2-3-4 clutch drum.

# 3. If only a new 3-5-Reverse drum is purchased without the bearing, purchase and install the bearing. Or, purchase a new 3-5-Revese Drum Kit which comes with the bearing.

Service Information:

3-5-Reverse Clutch Drum Bearing — 24226393

3-5-Reverse Clutch Drum Kit With Bearing — 24260894

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