Chrysler Repair: Autotrans locks up, stalls engine when stopping after long drive: 96 van, torque converter clutch, maximum air flow

Question
We had a rebuilt trans installed last spring, a new trans computer installed last fall, and it started locking up and stalling out the engine at the end of a two hour trip.  The trans shop admits to knowing little about elect prob's.  The car has 120+k miles.  The first computer they installed turned out to be defective.  The original trans prob was not shifting beyond second gear.  What could be causing the lockup?  Thanks.  

Answer
Hi Cliff,
The problem is with the torque converter clutch which should release as the trans shifts down from highway speeds. This clutch is functioning the way a clutch does on a manual trans, but in the case in order to reduce slippage when you are cruising and thus save gas. But it isn't releasing when it gets hot. You could try checking that the trans fluid is at the proper level (don't overfill and only use ATF type 3 ideally of Chrysler brand from a dealer). Then check to see if the front of the radiator/trans cooler is blocked with leaves/mud/debris so that you aren't getting maximum air flow to cool the fluid as needed to prevent overheating.
Then if that doesn't fix it, the fault codes should be readout on the the trans computer. Your vehicle was built just at the time they were transitioning from OBD I to OBD II so you will want to be sure to get the trans memory readout correctly. The code will either be read from a separate plug (I) or from a unitary plug (II) that also reads the engine computer. The former has two digit codes, the latter 4. I believe that yours will be the II type.
Ask what are the numbers, the names, what they mean, the fix, and how much $ if not covered by warranty? Then write back with the results and we can compare to the Chrysler shop manual.
I checked the wiring diagrams and couldn't find a specific wire for the clutch so it may be internally controlled by other components.
But see if the temperature issue might be the cause, and try to improve the heat dissipation via the cooler air flow up front first. If that doesn't do it, then probably the internal clutch mechanism is at fault but the codes may be the best clue for a strategy.
Roland