Recently my S4 (2001 about 55000 miles) started to make a noise when it hits 4000rpm in first in second gear. Does anyone know what this is, could it be the timing belt?

 

you need to give a litle detail about the noise since we cant hear it.... what does it sound like?

 

sorry, here's more detail, at 400rpm in first and second gear, there is a quick grinding or moaning sound. Because of the miles on car I'm thinking that this is the timing belt, but I'm not sure. There is no smell or smoke coming from the car when it happens, and it doesn't happen at 5000-7000rpm.