I was driving my car, 96 coupe LT4, today with the windows up. I can hear this sound in the car that reminds me of an AC system that is off on a 70s-80s GM car. That hissing sound. Or a dragging brake that is worn out. But it's neither of those as the brakes are new and they are not smelling like they would if one was stuck. Its not the AC system because when I open the drink holder the sound is louder. So I am thinking the transmission is doing something. Its a zf6 and I recently changed the shifter lever to a short throw shifter but I dont see how that would make the sound. Under 20 mph and you dont hear it. Above 20 and it starts only gets louder and quieter with the speed of the car. There is NO change in the sound with the application of the brake or changing the gears or revving the engine.

I have attached a video of the sound. This is about 30 MPH. You will need your sound up. If you guys need more video of it I can do that. I love driving the car. Finally got legal a few days ago.

 

Sounds like something is dragging on the flywheel or clutch pack. I would check the metal inspection panel first. Sometimes it gets bent and interferes with the flywheel around the rear main seal area. Any recent work done? Mybad. For the short shifter was the transmission moved or removed from the c beam?

 

The shifter doesn't require removal of anything other than the shifting mechanism on top of the transmission at the back through the floor from inside the car. I will check the flywheel cover for sure but I would think if that it would make that sound even sitting still since the flywheel is turning.

I had a thought, yes it happens sometimes, maybe it's a wheel bearing... The sound doesn't show up until at speed above 25-30. How can I check for bad wheel bearings? I know when I had one go out in my truck I rolled the windows down and drove next to a retaining wall and the side and area that echoed the loudest told me where to look. Maybe I will try this again.

 

While driving if you slowly turn first to the left and then to the right the sound of a bad wheel bearing will increase on the side turned to.

 

Off topic but was it you that installed the short shifter? Reason I ask is it is on my list of to do on my vette and all the videos indicate you need to remove exhaust from cat back and do some work underneath the car to install the shifter.

 

Yes I recently did this and yes you will have to remove the exhaust. You have to access the the connection point where the shifter connects to the shaft that goes into the transmission. You wont be able to get to it with the exhaust on the car.

 

This may be dumb, but is there any chance that the thick rubber shift boot (the one under the nice-looking one you see from inside the car) came loose or got torn? If that isn't sealing the hole in the tunnel properly, you'll get a lot more noise in the cabin. You will probably get more heat, too. It's amazing how much that boot seals out. That said, your video does sound like metal rubbing on other metal. I'd get back under the car and verify that the exhaust isn't hitting anything, and the same for any parking brake cables or anything else that is even sort of close to the driveshaft. If the sound only happens when the car is rolling, then it has to be coming from somewhere aft of the transmission.

To check your wheel bearings, jack the car up and try to wiggle each wheel with hands on top and bottom and left and right sides. If you get play (make sure it's not just slop in the unloaded suspension!), you have a bad bearing. If you do have a bad bearing, you might be hearing the brake disk rubbing on a pad. Does the sound go away when you lightly apply the brakes? Doing so will use the brake caliper to force the wheel into its proper plane even if the bearing is shot, and the sound should then go away. If it persists with light brake application, then it's probably not a bearing.

 

The rubber primary boot is new. It is sealed good under the leather secondary boot.

The sound doesn't go away with light braking. I will check the wheels with the car jacked up. I only hear it when the car is up to speed as well.

My friend named my car insatiable. It has an insatiable appetite at all times for anything that is in my wallet.