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Transmission Fluid Leak at the Drive Shaft Yoke

Gil’s Garage

Gil Baumgartner
CTCI Authenticity Chairman

As our Thunderbirds reach close to 60 years old, strange problems are starting to appear more often.

Recently I encountered a situation where fluid was leaking from the rear of the transmission. The owner thinking it was the rear seal at the output shaft housing – replaced the seal. A few days later the leak reappeared and the owner brought the car to my shop to diagnose the situation.

Troubleshooting found the fluid leak coming from the center of the drive shaft yoke (p/n 4841), from an area I’ve never experienced a leak, until now.

Photo # 1

Photo # 1 shows the yoke plug.

Our inspection discovered the plug that seals the end of the yoke had a small rust hole from the inside out. As the fluid traveled down the output shaft and yoke splines it leaked through the holes in this plug.

Unfortunately, the plug was never a serviceable part and is not available separately.

Photo # 2

Photo #2 shows the view from the inside of the yoke, looking down the splines.

As you can see, its much more obvious from this view that there is a larger area of surface oxidation on the inside of the yoke plug that could cause a much larger leak if left untreated.



Photo # 3

Photo # 3 shows the repair after the JB weld was applied and hardened.

The small hole was repaired with JB weld available from most auto parts and hardware stores. This can be accomplished by removing the yoke from the drive shaft, cleaning the area thoroughly; mixing the two-part JB weld and completely covering the plug area face up.

The JB weld will flow out smoothly and harden providing an oil resistant seal. This repair should last many years due to the fact that very little oil reaches the cavity past the spines.

Gil Baumgartner

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