That sounds like one of the cv joints broke. If you look underneath, you should see one of the two half shafts hanging down and there might be transmission fluid dripping. That will allow one of the shafts in the transmission to spin when you shift into drive or reverse. The transmission is going but it doesn't know that the car isn't moving. The grinding is from the parking mechanism trying to engage while the transmission is still coasting. In effect what is happening is the same as if you tried to shift into park while the car was still moving.
Replacing a broken half shaft is not the most serious thing to have to do. It can be done by a do-it-yourselfer but if you don't know how to do it, it's best left to a professional. A rebuilt shaft can be found now often for less than $100.00 but could run up to $200.00 depending on the car model and whether or not it has anti-lock brakes. These shafts rarely break without a lot of warning. The first thing to go is one of the rubber boots. That lets the grease spray out and dirt and water can get in. That will be noticed by the guys who change your oil. Later, as wear takes place, the outer joints can make a clicking noise heard mostly when turning and accelerating. You won't hear that noise when driving straight ahead.
In rare instances a spring inside the inner cv joint can break and allow that housing to pop out of the transmission. The spring pressure is what holds it in place. That can happen without warning but it isn't real common.
Monday, April 18th, 2011 AT 10:30 PM