It's due to wear in the valve body bore around the TCC PWM valve. Thread closed due to necro-posting spammer. I'm thinking that the worse likely problem is that I wear out the clutches for lockup and end up having to replace the torque converter. My biggest concern is that we're headed for a 3K trip from Utah to Dallas and back and I don't want to cause any additional problems, or especially suffer a catastrophic failure along the way. I know there are other problems that I could encounter, but I don't expect to own this vehicle much past 200K miles, and don't want to sink a lot of $$$ into it. I really don't want to pay a transmission shop to tear it all down to do this, as I'm sure they would recommend a full rebuild.
Has anyone experienced this? I know you can buy a new "liner" for the TCC bore after it has been reamed out. The problem goes away at around 65 MPH and above. There has been no trouble code recorded yet for slippage, and even though I can see it on my tach and hear it in the drone of the engine (lovely straight 6 exhaust note), my AutoTap ODBII which has the "enhanced GM diags", never shows a slip value above 1 or 2 RPM. I also know that this is a PWM lockup, however this particular condition is new and definitely different than it used to behave. I've heard that there is an issue with the TCC valve bore wearing and causing a pressure loss. About 10K miles ago, I started noticing that at lower speeds when the torque converter should be fully locked (50-60MPH), that it will lockup like expected, but then there will be a couple seconds of slippage, allowing the engine RPM to increase 200-400 RPM, and then back to full lock. It has been flushed (draining by opening the cooler line while running until it just runs out and them immediately stopping the engine, filling 4 quarts, and repeating 3 times), and the filter replaced at 50K intervals with non-synthetic oil. It has the original trans with a secondary stacked plate cooler added. I have a 2002 TrailBlazer 4x4 with 174K miles on it.
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