Transmission shifts funny from 35-55 if under a slight load. Shifts fine if not under a load and seems to shift ok too if I'm rapidly gaining speed opposed to gradual speed gain.It would jump back and forth when trying to upshift, if I tried to gain speed it evenually shifts up ok and runs fine. Gotten more pronounced the past week or so. It is fine at slower speeds even climbing a steep street. I'm really hoping this is not serious. I put 1/2 qt of fluid in it because it was low but did not help. Could it be a modulator? No engine light on or other lights. Seems not to happe I did try putting a pencil in a loose vacuum line but the car shifted even worse then throughout the whole shifting range. Thanks Very Much
Loose vacuum line and transmission not shifting properly on 1997 Oldsmobile Regency
by PensFan in Crescent, PA on January 13, 2010
ANSWER by Bret Bodas , January 13, 2010
If this transmission has a vacuum modulator, then make sure the vacuum supply to it is good. Fix any vacuum lines by replacing them, don't disconnect or plug any of them. Hope that helps.