I just had the rear main seal replaced as well as the plate since it was chewed up. I have now noticed that after the car sits over night when I first start it I get this annoying shudder/vibration that appears to be coming from the transmission. If I switch through the gears it slams into 1st gear when I get there. I only notice this behavior after first starting the vehicle. Otherwise the tranny shifts smooth as butter.

Any thoughts or suggestions on what this might be?