I have a 94 A4 t/a and out of no where when i put the car on D it would make somekind of grind/crack noise, It wont do this when i put it in reverse. It also does the noise when it shift into 2nd gear while going at high rpm.

 

Is there a light Thumbing or hammering underneath the car right where your shifter is cuz if there is it might be your tranny mount

 

I 2nd that one it does sound like the trans mount

 

I recently replaced the tranny mount, but im hoping it is again. This time thought it maked more of a grindind/slap noise, instead of a bump to the bottom of the car.

 

I went through 3 tranny mounts in a 2month period from AUTOZONE and I finally went to PAW and purchased a Polysomethingsomething (its a rubbery one) and never purchased a tranny mount since and this was about 3 yrs ago.
By the way, the last tranny mount that I replaced was cracking and it still made a light thumping. You might want to check out first.

 

polyurathane...

and it could be a tranny mount but a bad bearing can also cause a grinding noise but i'm not so sure its that. grinding noises are usually more common in manuals than autos...