[jpyounis1]

i def hear you. wouldnt want to start a rebuild if its just the computer..

well, did u take the TCU out?, if not id take it out. its under the center console by the accelerator pedal if you didnt know. behind the ECU.
remove the top, check for leaking capacitors, and if it smells like fish its toast. Since you have a 98, im not thinking this will be the case, but its a easy one to rule out...another thing too, check the 2 connectors in the engine bay, right on top of the the transmission. make sure the wires and all the connectors are still intact. corrosion or a loose wire can cause a problem similar to this with the pulse generators.

in the past when ive done work on auto trans at my shop, sometimes its very possible for a fried TCU to cause issues like this, as the oil pump may not be pressurizing properly, or the TCU isnt sending the correct impulses to the tranny solenoids. etc. but id rule the tcu out of the equation with ur symptoms unless the caps are leaking.

I believe you need the mitsubishi MUT-II scanner to view the trans codes. but im not sure. maybe someone can chime in.

in this case man, im going with worn clutch packs. the bad clunk was probably a loss in fluid pressure, which put the clutch packs into stress enough that the trans kicked it self into safe mode.

IPT is your best friend for our auto's. give em a call. their shift kit may be of interest for u too. good luck