Cadillac Repair: Code 741, torque converter clutch, torque converter clutch solenoid

Question
I have a 1999 eldorado Cadillac.  Service engine soon light came on about one month ago.  I had my mechanic check.  He hooked a diagnostic hand held machine to it and got (2)codes.  One of which I do not remember, but had something to do with the gas cap not being on right. Also 741 something with torque/transmission clutch. Did not know which of the two it was. He told me to drive it and see if the light came back on. Light did not come back on till driving back from PA about a month later.  Upon 2 more days of making this 4 hour round trip, I took the car back to my mechanic.  The only code that came up was 741.  Something to do with the trans clutch which could be any of about 7 different things. Light has not come back on yet.  Car runs no different than before.  I always put high test gas in.  Never midgrade or regular. I am also told that unless the transmission is taken apart, which will cost approx. $2,500, it can not be detected as to what the actual problem is.  With everything else in this car, I would think there is some kind of test to be able to pinpoint the exact problem.  I would hate to spend that money only to find out it was a $25 sensor. Is there some other way I can find out exactly what the problem is without spending this high dollar amount/

Answer
Your problem is that the TORQUE CONVERTER CLUTCH SOLENOID which engages and disengages the OVERDRIVE in your transmission is intermittently sticking in the OFF position thus causing your overdrive not to work.

This is a very common part failure which can be replaced for approx $800.00 at most any repair facility.

If you would like pictures and the solenoids exact location in the transmission, You will need to e-mail: onlineautohelp@msn.com