97 Lumina transmission shifting problems

The transmission shifts fine in all gears except when shifting into overdrive at @ 50 - 60 MPH. It will shift into overdrive but its not smooth and it just kind of lugs into gear. After it goes into gear it does fine. Any help would be greatly appreciated.

Age, mileage and condition of the the trans in general are all part of the issue. Without a full trans scan and road test this cannot be accurately diagnosed

Thanks.