e34 groans and whines....

Hi.

before i let the local mech loose, any comments about the following symptoms
occurring on a 1989, e34, 530i se auto. only when i set off and until i
reach about 30 mph i get this groaning/whining sounds coming from the rear.
sounds not unlike something in need of lube or being strained. my first
impressions - rear suspension, exhaust or maybe something to do with the
auto box...?

i know it's a wee bit vague but any ideas/follow ups appreciated.

tia

mojo