I have a 2002 Chrysler sedan with 113,000 km on it ( automatic trans. ) It now jerks & has a clunk when it shifts down from 60km ,What's my problem ? It didn't do this before .

inspect the drive axles for tearing of the boots and leakin' out the poisonous grease, then the CV joint gettin' sloppy~

https://www.google.com/#q=2002+Chrysler+Sebring+axles&tbm=shop

I am wondering about the solenoid and also told that their are bands that possibly could be adjusted ?

there isn't a way to "tighten" a broken ankle...this is what you're asking~

should get a transmission service in which they'll drop the pan and check the magnet for shards, change the filter and the fluid (torque converter too)....as far as adjusting bands...have no personal knowledge of how this is done but would research this if you ask me to~

Set the parking brake, open the hood have a friend observe how far the engine moves forward or back when placed in drive, if the engine picks up more than an inch it needs engine mounts front and back check the mount on the passenger side at same time