Howdy, I just got a '98 automatic trans put in my '96 outback wagon. Do I need to put a '98 ECU in there as well? the car runs fine but I notice a slight vibration/ hesitation when accelerating from a full stop. thanks!
The Phase 2 transmission didn't go in until 99 models, so unless your "new" transmission came out of a 99 model manufactured in 98, it should be operable with the same module. To find out what model your transmission is, you need to get the number from the sticker on the transmission bell housing. Unless you know the exact car it came from, then you just need the 10th VIN digit to determine year model.
Did you replace the torque converter?
New fluid and filter?
Clean throttle body?
All the plugs are tight?