1989 Auto transmission question
 

When I shift from "Park" to "Reverse" and/or "Neutral" to "Drive", the transmission seems to slam into gear, not a gentle shift like my other vehicles but a hard slam that seems like it might hurt the transmission. When I drive it, it shifts smoothly between gears but it's the initial shifting that will jar your teeth. I've heard about kickdown linkage etc but I don't know how to adjust it.
Any help?