jumpy shift

2000 century, every once in a while; quite rarely, but a matter of concern
shifts hard, kind of jumps from gear to gear; what could cause this?

It would be helpful to post your mileage. When was the last transmission service performed? A common problem causing hard shifting in a 4T65E autotransaxle is the PCS solenoid.

81,000

How about the transmission service? When was the last time the ATF and screen filter were replaced?

The Century forum has alot of info on PCS solenoid related issues. Just do a search. "PCS solenoid" But I would start with the easy and inexpensive things first.

transmission service has not been done yet
you think that could take care of the problem?
Thanks very much for your input

Hopefully but no guarantee. What is recommended is a pan drop service consisting of replacement of ATF (Dextron-III) and screen filter. Shops will most likely do a flush either full or fluid exchange but I would exercise caution. Many of our members have reported worse problems or total failure after a flush. Good luck.