I have a 95 4.3L Z code motor with 4L60E (believe that is correct designation) 4 speed auto trans.

Under hard acceleration from stop, it shifts from first to second but hangs in second. Sometimes feathering back the gas MAY get it to shift but more often than not it stays in second until I stop and accelerate normally.

Under normal to moderate acceleration it shifts fine through all the gears. It will downshift under load and shift back up the gears with no issues.

No clue on these electronic tranny's so any help would be appreciated.

Thanks, George

Try adjusting the manual valve (kickdown) cable.

also check you fluid level. refer to the manual for proper procedure.