I drive a 740 wagon with 243k miles, and an AW70L transmission.

Last week while driving at 65 MPH on cruise control I noticed that my torque converter (TC) was no longer locked up - my engine speed (RPM) would increase going uphill.
I was able to drive the remaining 20 miles home. However the torque coupling provided by the TC gradually decreased to the point where it was difficult to ascend a moderate grade.

The transmission fluid (Dextron III) was fine - appropriate level, bright red color, not burnt, or hot during operation.

When the transmission is in park and the engine idling, here is now a whining sound coming from the area of the TC.

It will drive OK for about 5 minutes at a time. The coupling provided by the TC gradually decreases during this 5 minutes. If I stop and shut off the engine for about one minute (not long enough to cool down), the function of the TC is restored, and I can drive for 5 more minutes before needing another 1 minute time out. I have thus driven around town for the last few days. The vehicle is now on jack stands in my garage. I've drained the transmission fluid, and I plan to drop the transmission and extract the TC today.

I have ordered a reconditioned TC (part VO20 from Transtar). This will replace the TC I purchased from them 15 months (and 15k miles) ago. They want to slice my current TC open and examine it before we discuss their 3 year warranty. This is the 3rd time I've seen the TC converter fail on this car in 16 months with similar symptoms (the first two TCs with high mileage).

I invite folks to comment on the following:
1. Could the symptoms described above be anything other than a bad TC?

2. What specific failure might have occurred within the TC?

I will eventually post a comment on this thread with results from my TC replacement, and Transtar's findings.

John Mattox