Strange noises from back of car

[magnumlove]

I know this is none e30 related but still appreciate some advice. Anyway, someone at work today advertised a 1992 e36 318i se for a ridiculously low price. However they stated that the auto box is making a 'grinding/clunking' noise so is probally on it's way out. Took a look at the car which was in good condition and upon testing driving it, the griding/clunking noises came from the back of the car, I suppose almost underneath the back seat. However, it only happened when the car was acelerating and when it changed gear. Would this be the diff or is it down to the auto box? Cheers

[bellgtti]

might be thediff donut or diff shells

[magnumlove]

are these expensive to repair?

[bellgtti]

donut isnt not sure on diff shells or the autobox tho