When i put the car in to reverse there is a loud thumping comin from under the car. I think it is the driveshaft but i just replaced the old one. Any ideas

 

How's your transmission mount? What clutch do you have?

 

It is an automatic transmission stock

 

Could be the y-pipe banging against the floorboard. Do you have the stock or aftermarket y?

 

I only really hear the noise when i am going in reverse and i noticed when i was changing the pads on the rear of the car that the passenger side axle just slipped right out of the dirrerential so i dont know if that is the problem and i have to replace the gears or what.