It's a real helicopter following you around, man; put on your aluminum foil whirly-bird-beanie immediately and stop accepting cell calls! Better yet, ditch the car and run for your life!
No... seriously, here's the countdown to diagnosis of "THE HELICOPTER NOISE":
1) First off, "IF" your motor mounts are really bad, they can distress a bunch of stuff which spins under there. They love to bind and break stuff, while you corner at 70, around the off ramp from hell.
2) If your steering controls are bent, worn, or binding, ^^^, they can cause a grumble or two and bearing destruction. You can roll it down a hill in neutral and tell if it's the steady grind mentioned above.
3) Bad C/V joints tend to rumble when they are dry, especially the outer race. It will cause bump steer and add to the bending of the steering controls, if it is shot. If the inners are gone, you are really going to be surprised when you open the boot, yanking it out of the trans side. Crumbs.
4) Lower Ball Joints will eat the CV joint and so the damage may be compound. The rubber axle boot is flopping around the axle. (Not likely. The rubber boots are thick, when they break they usually don't disintegrate or fly apart).
5) Axle Nut is loose. This is a doozy. Loud helicopter noise! Your tire is wobbling around like clown tires!
6) The $uper cheap drilled and slotted disks you bought off eBay got warped to hell from hard braking and splashing through ONE big puddle, so now your disks are warped like your sister's BeeGee's album, after you left it on the stove for ten minutes.
7) The small plastic surround over the wheel well broke free and is bound up under the transmission, where it co-incidentally covers the driver's side axle.
8) Something you ran over is caught by the trunk or is sticking out of the vent flapper and digging into your bulging clown tires, shot from slamming curbs and running over the kids bike, last week.
9) When you tried to yank the replacement drive axle, last time you changed your CV, you decided to use your pry bar to pull it out one time and bent the seal around your Transmission side seal, which is now mutilated and grinding the seat of the transmission case or the seal.
10) The carrier bushing on the passenger side is rubbing the hell out of the drive axle, which is now badly crumbling and will fall out in bits, when you take it out of the spindle.:o
11) It is entirely possible the weights on your axles are flying around, as happens when the rubber decays or the bands break, allowing the weight to scramble around the axle.
12) Someone tied a length of rope with a few nuts around your axles just to make you freak out. Been there, done that.
13) Your brake bracket was never tightened properly or the bolts just snapped and now your caliper is hanging on by one bolt.
14) Your caliper piston stuck months ago and now it has worn out one side of the pads uneven. Major grinding noises will be in your future.
15) Your old rusted E-brake cable has broken free, your drum piston shot out one side or another, the spring pins are shot, so now chunks of rear brake parts are digging into your brake drum, every other spin around the axle.
16) Your wheels are bent and hitting your springs from side-swiping the curb, nearly flipping the car, when you tried to park your car like that really cool commercial!
17) Yes that was a DEER! Now your carrying carrion and it's reaching escape velocity.
And the last possible excuse for helicopter noises is...
18) Your Big Brake conversion, included stainless brake lines, which are now rubbing the inside of your tires. You didn't realize the lines need room to move and to be zip tied in place; just right. Unfortunately, you will be blowing brake fluid all over your tires, as the reservoir runs out once you cut through the stainless.
I'm voting for number 18. That's what my helicopter noise was.
Bolted up me Big Brakes and drove it like hell all day, even though it sounded like a helicopter. Figured I caught a road kill, plastic shopping bag or something off the road, around the axle. LOL
(The SS B-lines really should come with zip ties and a "hey stupid warning" in the kit).
Thanks for shipping me those emergency Stainless Teflon brake lines GREG V!