1999 Jeep Grand Cherokee Limited downshifting issues?

My 99 Jeep GC limited transmission is acting up when coming to a stop or slowing. It tends to downshift somewhat hard. Wife felt a continuous jerking when coming home tonight through the neighborhood. Fluid level is good. I test drove it and it drives fine on the open road (55+) but when you slow down it'll downshift hard ( you kinda hear and feel a clunking noise when this happens), not always though, this seems to be intermittent. It would seem I bought a lemon of a used car. Anyways, all and any info would be greatly appreciated. Thanks!!!