After reading through the Forum I can see that nobody is reading the service manuals or the transmission manuals. The 61 through 63 had “Hydra-Matic” transmissions, not “Roto-Hydra-Matic” or So called Slim-Jims. Oldsmobile only called them “Hydra-Matics”. People put all the other names on these transmissions. The 61 F-85 had only 3 speeds in their automatics and the 62 and 63 F-85 had 4 speeds in their automatics. I haven’t driven a 61 so I don’t know the feeling of the shifts but I do know that the 62 and 63 automatics when shifting from 1st to 2nd you could not feel the shift but from 2nd to 3rd you could feel it shift and also from 3rd to 4th. If you left the lever in “S” the transmission would shift into 4th at about 65 MPH on its own without you moving the shifter but when you slowed down it would also down shift to 3rd it you didn’t move the shifter to “D”. This was a safety built into the transmissions so they didn’t blow up. According to the 62 manual if you leave the shift lever in “L” it will not automatically shift beyond that point. If anyone has a service manual or any manual that refers the 61-63 F-85 transmission as a “Slim-Jim” I would like to know about it. I am not sure but I don’t think Oldsmobile called any of the 60’s transmissions “Roto-Hydra-Matic”. I know that Pontiac called their 61-64 Pontiac Hydra-Matic transmission – series 10-HT “Roto-Hydra-Matic” but I’m not sure if that was the Tempest or the full size or both. All of the above is out of the manuals and fact not word of mouth.