97 4T60E will take off in 1st wanting to somewhat slip which it doesn't really feel that way, it'll hang up in 1st allday til I feather the pedal causing it to shift into 2nd, than 3rd works fine, shifts into OD at about 45mph. Cruises 70 mph down the road in OD staying in gear and partial throttle will accelerate like should, soon as your into WOT it'll just slip and rev the engine up nomatter what gear your in... I just changed the filter added fluid plus some Dura Lube... what would cause this symptom? Does not have no vacuum leaks what so ever swapped modulators and check the filters for the vacuum all good..
