I have just bought this Ford Mustang GT. It's my first Mustang. I personally have replaced Motor mounts, Transmission mount, new tires, rear upper and lower control arms and bushings, removed the quadra shock system, transmission filter and gaskets.

What I have is a hum and high resonance vibration at the speed listed in title. if I let off the gas, it stops while coasting, as soonas i get back on the gas it begins again. If I gun it through to 80 plus it seems to go away. The vibration/humming can be compared to a jet engine noise like when flying on a commercial airline. I cant figure out what it is. I have an Automatic GT. Any ideas?

 

could be gear noise from an improperly set up differential do you know if there has been any work done to it?

 

I'm not sure but maybe because the speedo is off. It's driving me crazy but I want to narrow it down instead of throwing parts.

 

Rear gears sound logical if it is "whining." Otherwise it could be a horrible mis-fire, might need to do spark plugs and wires. But if the sound is coming from the rear of the car It's more than likely the gears.

 

It's like a deep humming sound. Can't really pinpoint where it's coming from. Only between 60-80. If I put in neutral while riding it stops or if I back off the gas it stops its only when I give it gas in that range.

 

Wouldn't it still hum in neutral because the rear gears are still spinning going down the road

 

deep humming sound....exhaust drone?

as for the gears, yes it can still whine in either drive or coast or one of the two

If you want to try to isolate it put your rear end on jack stands and have someone run it up to the speed where you are having the problem and listen under the car...

 

Sounds really dangerous! I wouldn't get it up to 80 on jack stands...

 

It sounds stupid of me to reapeat what everyone else is saying but it is the rear end, you need to check or have someone check the preload of the pinion gear. It does it only under acceleration because that's when the pinion gear is forced against the heel side of the ring gear, on decel and neutral it doesn't do it because the pinion gear is resting against the face of the ring gear. Have you preload adjusted properly and it should go away. The only reason why you hear it at that specific speed is because of gear reduction, causing your rpms to be low, it probably does it in every gear but you only hear it in overdrive. I really hope that helps! Nick, Apollo 2v

 

+1, that would be my first guess based on the OP's description. When I got my '03 the kid that had owned had installed an o/r X pipe and Flowmasters welded into the stock catback. The drone at 2100 to 2200 rpm was so bad I could not stand it and replaced the exhaust system the 2nd day I had it.

Like others I am not wild about the jacking up the car bit...