Transmission shorting battery when stopping slowly?

On the last transmission downshift at residential 4 way stops, and slow stops like parking, a 60-70 electrical power loss happened: dashlights dim/headlights dim/ac fan drops/ big engine sputters, all at same time. The past few months only occasional very minor symptoms occurred. Recently upon restart with full electrical power, starter would not turn over, gearstick was locked, and steering wheel was locked. When wipers were bumped on, the gearstick released but still no starter turnover happened, and dashlights/headlights stayed strong. Next day it started once. It idled ok but had no starter turnover when I tried to restart. Also recently, a first time clunk in transmission down shift happened from about 50 mph to 40 on interstate coasting slowdown. Hasnt repeated.