2001 Subaru Outback Does this seem right?

I have a 2001 Subaru Outback Limited with 48000 miles on it. It has been serviced regularly. It makes a whrring, kind of grinding noise when you accelerate. When you take your foot off the gas, it bucks a bit. It also idles rough and stalls. I took it to the dealer, and they said the technician found metal shavings in the drain plug of the front differential--and suggest I get a new transmission. It seems ridiculous to me. Does this seem to be a correct diagnosis? Thanks.