When I let off the gas and also when I decelerate like coming to a stop, I hear this whining noise but it isn't constant. It sounds something like err err errr errrr errrr. It gets longer the slower I go but I'm not sure what to check first. I'm going to swap the tranny and rear end fluid this weekend and see if that helps but I don't know where to go from here.

 

It could be a bad pinion bearing in the rear axle. Put the trans in neutral, with the car up on jackstands of course, and see if you can wiggle the pinion yoke. Also feel how much backlash it has. Then report back.

 

Im currently at school and I wont be able to work on it for a couple weeks but I'm hoping to figure it out before I go back, How do I know if there is too much play in it?