HELP! Tranny problems

[Cypher5150]

Every since its gotten cooler in my area I have noticed some strange things going onwith my 95 240. First, In fifth gear anywhere above 70 mph I let off the throttle and I hear this high pitched screeching sound from under my B&M shifter. It only last for a second or two but its really getting nerve racking. It only happens in fifth & at those speeds or higher. We replaced a clutch about 6 months ago, No fluid leaks & we used synthetic to smooth out the shifts. Could it be that the fluid is to thin for cold weather? Temp has been around the 30s to 40s for the last month. Also I am hearing this humm from the what seems to be the passenger rear( its hard to tell for sure). This starts around 20 mph and up. It never gets louder, But its there. Its also more evident when you are coming to a stop from 20 down. I raised the car up and ran it, no hummm. My thought is bearings. Any other ideas? Thanks in advance!