alright so my buddy just took my car and did an alignment for me and he told me that i had a heavy leak in my transfer case. im pretty car illiterate but im not trying to take the car to audi, weird though because i took it there less than a month ago and they said i had no other problems than what they fixed...

my question is where do i go from here, is it an easy repair, how do i go about diagnosing this?

also is this something that happens over night or does it wear over time

thanks