Engine Problems?

I have a 2000 Audi A6 2.7T and recently the engine is not working right. after coming to a stop I will step on the gas and the gears wont get caught to turn the wheels. Instead the engine revs and the car rolls until the the wheels work. I am thinking this can be a transmission problem but I really dont know. Could it also be the timing belt?? please let me know if any of you encountered a problem like this before and if you solved it.

Tranny issue. No engine codes, right?