Basically what happens is the following:
1) When I start the car in the morning or after it has completely cooled down it starts normally, no noise or anything unusual. When I put the gear on R there is this grumbling noise I hear, or when I put it on D and turn the wheel to get it out of the parking spot I also hear that noise.
2) Once the car is warm I stop hearing this noise, but I sometimes do hear it when turning the wheel while driving, but much lower than before.

Any ideas as to what may be the cause? Thanks.