I just replaced my damper on my 322. Mine was definitely shot, but it really didn't make it much better. When I replaced my 318, it made a huge difference. Anyway, not too expensive and not too bad to replace.
Hopefully the 1990 will have the better damper setup near the rear differential. I had to upgrade my 1988 322 to this hydro version. My damper was in the dash tower and I didn't like that version. You should be able to see the damper on the right side when looking through the rear of the machine. It's likely bad and will cost you around $84 online (P/N is AM121646). The other potential items will be loose or worn linkage parts. I just replaced a damper on a 1992 318 this year and before replacing it was pretty bad.
My 1992 322 also had a 'jerky' behavior responding to changes in the ground speed lever position. If you do a search on "jerky hydro" you will have plenty of reading material. In addition to the possible worn dampener, any play in the linkages will also magnify this symptom. Inspect for wear at every joint and pivot in the linkages...renew or repair as needed. Many of the threads you will find in the above search have good pictures of what wear you might expect to find.
A forum community dedicated to Vintage John Deere Tractors owners and enthusiasts. Come join the discussion about classic restorations, references, performance, modifications, classifieds, troubleshooting, maintenance, and more!