The transmission pressure control solenoid may fail causing erratic shifting. Our technicians tell us that partial dis-assembly of the transmission is necessary to replace a failed pressure control solenoid.Google+
Car Problem Reports
Buick Riviera Transmission Pressure Control Solenoid Failure May Cause Erratic Shifting
Buick Riviera Problem
Average Mileage: 143,200 mi (112,000 mi - 160,000 mi)
Visitor, 1998 Buick Riviera, 112,000 mi
Sometimes it shifts like it has a shift kit in it and other times its super smooth.