With AC on vibration in front wheels at 45 mph

When I drive my 90 acura sedan down a hill from 50 to 45 mph with the AC on the front end shakes and the steering wheel vibrates. Without the AC on the car doesnt do it. I know around 45 is where the car's automatic transmission shifts. My other car a 89 coupe doesnt do the shakes at 45mph with the AC on. Anyone know what could cause this problem. Can it be the shift solenoids or a sensor. I don't see any flashing led's on the module under the drivers sear or the passenger seat either. Otherwise with the AC on the steering is fine only when its in between shift points.