would an ecu off a a/t work on a m/t
 

would an ecu off of a 91 a/t work on a m/t truck

Pins may be different.. need to look up the pin out on both. After 1988.5 there was a bit of variety in ECU pin out... esp auto vs manual.

There would be a problem with the computer looking for the tranny and not finding it.

my buddy did a 5sp swap and didnt swap ecu. the speedometer didnt work and it would throw a CEL.

what do you mean by cel what is that?

check engine light (cel)

seems to me somebody did this a while back and it turned out ok, but they had to trick the computer into thinking the auto was in N

Makes sense. The auto trannies have speed sensors......number one happens to be at the back of the speedo.

I've done this on a 88' Toyota MR2 and all you have to do is jumper 2 pins so it thinks its in neutral.