Saturn transmission

I have a 2002 Saturn SL and four months ago I replaced the transmission control soleniod. I had no problems the car shifed smooth and quiet until yesterday. The same problem again. Any advice?

Thanks

Have you checked the level and the color of the transmission fluid?
If not, that is where you should start.

Yes, the fluid level is normal and was changed 6 months ago. The color is normal and no burnt smell.
Thanks