Own98 BMW 7 series, what are symptoms of a weak rear suspension--what does one test for--local BMW mechanic says supension is dangerously close to failure while BMW dealership says nothing wrong w it

Check the condition of the wheel bearings, struts, dampers, sway bars links, sway bar bushings, control arm bushings, and a lot more on those multi-link suspensions. There's a lot to them. Basically, every 100,000 miles the suspension systems (front and rear) need a lot of attention. It won't be cheap. In the long-run, it's cheaper to get everything done at once. Go with top-quality parts; e.g. BMW, Timken, Energy Suspension, and Moog.

Unusual noise, tire wear, handling, dampening, vibration, bounce, and lack of stiffness are general signs to look for. To the untrained eye, everything may appear fine, when it's not. Get a third opinion, if you're still concerned.