PowerTrain Pro: Automatic Transmission

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That was too easy

Tuesday, March 19, 2013 - 11:47
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With a lift now available, the truck went up on the hoist, and I immediately saw a water problem. Evidence of dripping water from the A/C system stained the converter housing causing rust all around the area where the harness plugs into the transmission. As soon as the harness was unplugged from the solenoid block, an ample amount of water dripped out of the connecter. Upon a closer look at this connector, two pins from the solenoid block remained inside the harness connector. Once I removed the solenoid block, the terminals that separated from the block were identified as the power terminal for the solenoids and the ground circuit for the TCC solenoid.

The combination of water in the connector and two compromised terminals in the solenoid block caused the erratic amp readings. It’s a good testimony in that doing resistance checks does not always discover a problem. In this case, putting the circuit under a load flushed out the problem (no pun intended). If I had a scope handy to do the amp checks with, I might have been able to catch greater detail in the fluctuating amps due to the power terminal having a small surface connection where it was corroded at the base of the solenoid block. Nonetheless, it was interesting to see how the amps presented themselves under such conditions.

Obviously, had I been able to put this truck up on the hoist right away I would have made this discovery immediately without having made all of those circuit checks. But seeing how these checks can be made so easily, it can be helpful to know these procedures when dealing with a problem not so easily discovered.

This water intrusion coming from the A/C system can be corrected by inserting a makeshift shield under the system to redirect the water to a more suitable location.

This water problem can cause internal transmission failure as well. With the transmission removed from the engine block, there is evidence of water dripping down the back of the block between the cylinder heads. The water was collecting in the transmission converter housing where it mates the block. There was a waterline mark in the area of a hose. This hose is the transmission vent. This hose originates from the extension housing and is purposely routed to the front of the transmission. This arrangement now allows this intruding water to enter the transmission contaminating the fluid.

This is yet another good reason to insert a makeshift shield to be placed under the A/C system redirecting the water to a more suitable location. What you do not want to do is cut the hose short of the front of the case and stick a vent cap into the end of it — this is not a safe solution. This hose purposely is placed so that should the transmission fluid ever vent out, it will not be a potential fire hazard hitting the catalytic converter. Instead it will dump into the converter housing and safely drip out the bottom. Though someone might mistake this to be a front seal leak, it is better than to make the mistake of seeing the vehicle go up in flames.

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