99 Sebring downshifts hard at 30 mph

I have a 1999 Chrysler Sebring convertible that downshifts hard consistently at 30 mph. I’ve been advise to change a solenoid pack as a first step before having a mechanic tear it apart. Any advice on this problem?

Before you go throwing parts at it, have you scanned the computer for codes yet?? If not, I highly suggest it.