Can be a number of things, the first thing to check would be the Subframe Bushes
There are many reasons as to what may cause a roaring noise in a rear end 1997 Infinity. However, this could be the brake system or needing a new catalytic converter.
that could be a variety of things, wheel bearings, u joints, rear end...
Brake linings worn out or wheel bearing is bad
Front Rear End? Does that make sense? Front differential? maybe? Low fluid, wheel bearing, choppy worn tires?
Bad shock mount? Loose exhaust system?
If it is in the rear end you need to change the third member oil.
Is it a "knocking" noise? or more of a..."grinding" noise? Does it sort of hum at higher speeds? If so, assuming you have the aluminum Dana 44 axle (which SHOULD be in your vehicle), then water or condensation probably got in to the rear end. This pits the bearings and makes a lot of noise. Not much of a concern, as long as you don't mind the noise. IF IT IS A POPPING, more like suspension parts, you should definitely have that checked as soon as possible. It could be bad/worn/loose shocks, or it could also be worn track bar bushings/end links. That problem is more serious and should be researched and repaired ASAP, especially if you drive at highway speeds. Good luck and hope I helped, -Dayne
Worn front axle and/or front end component.
If it is a rear wheel drive vehicle it is either low oil in the rear end or an axle bearing. On a front wheel drive vehicle it is probably a bearing.
#1 noise....loose exhaust
replace the rear shock asorbers
i don't know if it helps, but my '99 legacy outback was making a knocking sound. turned out that the oring on the brake caliper pin had worn out, and the pin was kind of knocking around.