Skip2MyPou

I need help identifying a squeaking problem asap. When decelerating (only in gear) from 50km/h and under, my car makes a loud pulsating squeaking noise which gets slower as the car gets slower, and vice versa. Also, the car makes the same squeaking noise when reversing. It seems to be coming from around the tail end of the transmission or possibly the front u-joint of the driveshaft. Could it be the u-joint?