1999 Voyager won't start ! Help please?

As stated in the thread title I have a 1999 Plymoth Voyager w/ 185,000kms.

I've just spent $1000 on the tranny itself and up until yesterday it was running fine (even the previous evening when I took my gf home). To my dismay the morning after I couldn't start my car (it would ignite and turn on but the engine/tranny would make a rumbling noise and the car would simply turn off). Stupidly, I repeated w/ trying to start the car and eventually it stays on (rumbling still existent) - well not until I change gears, once I go into reverse and/or drive the car again ceases.

Can anyone diagnose this problem or be of any assistance? I've gotten the car towed to my local mechanic as well and even he can't troubleshoot!!!

I hope the grand I spent on the transmission wasn't a complete waste. :banghead:

Is the Service Engine Light (SEL) coming on? It indicates a fault code has been set by the Powertrain Control Module (PCM), the engine's brain. On or off, I would try the key dance to see what pops up. Cycle the key from off to on three times, leaving it on (not start). Now count the flashes of the SEL. All codes have two digits. Digits are separated by a pause. Multiple codes are separated by a longer pause. For example, a code 21 would be flash, flash, pause flash. Should finish with a code 55.

Why was the tranny changed? They should have changed the torque converter and flushed the tranny cooler. Did they?