Chrysler Repair: transmission:torque converter lock-up chatter, shade tree mechanic, valid diagnosis

Question
1994 Chrys concord. between 35 and 40 mph the drive train shutters while under load. My shade tree mechanic says it is a problem of the lock up not engaging. If I keep it in '3' until reaching 50 mph it works ok.
Is his diag right and what is the resoultion?

Answer
Hi Ken,
That would appear to be a valid diagnosis. There are two things that would be worth considering;
first, check the fluid level on the dipstick. If any is needed add only ATF +4 and don't overfill.
second, would be to try to reprogram the clutch function via the transcontroller, using the Chrysler DRB II code device plugged into the blue access plug under the dash. It is supposed to be used when a new torque converter is installed for proper 'break-in', but I would wonder if it might not also sense the situation and make an adjustment? You could ask a knowledgeable trans shop that has experience with the Chrysler 41TE whether there is any hope of improvement that way. In any case, it is just a 'plug and play' that should not take much labor time to try, as long as it won't make things worse. And you could see if there is any other trans fault codes stored in the memory (other than a 38, the clutch code) while they are using the DRB II. If you happen to be in the SF Bay area I could run my DRB II on it :)
If not, then working around it (by accelerating thru the 35-40 mph range) may be the only alternative other than removing the trans and replacing the lock-up clutch on the torque converter. It would probably be more cost effective to wait until something else goes wrong that requires work inside the transmission too, rather than have to remove it twice. These 'beasts' seem to have a limit before they need a rebuild.
Roland

Hi Ken,
I hope everything workes out with the torque converter lock-up.  Please let me know by using the 'thank/rate' tab below.
While you are there, if I might ask a favor: where it asks about a 'nomination for expert of the month' I would appreciate your entering a 'yes'. I am in a close race for that honor so every vote counts!
Roland