for the same year trannys, yes the outputshaft is the only difference. the 4wd 4L60E did use a K case, but so did some of the 2wd. the difference is the way the inspection shield bolts on and what its made out of. some say the bellhousing is thicker, but the only thickness difference ive seen is where the inspection cover bolts on, it is thicker on a k case.
in, IIRC, 96, they changed the case to a 2 peice case with a removable bellhousing and an inspection sheild like a manual tranny. the adapter or tailshaft pattern was also changed to what the th400 and 4L80E has. hardly anything internall was affected by this change.
the output shaft between the 2wd and 4wd has changed from 1982 to now. except that the governor gear is not there on a 93 and newer tranny. there are a few differences between years and models on the 2wd shafts, but the 4wd shafts are identicle.
