Imagine taking heavy grit sand paper to a steel tube and swiping it back and forth to a drum beat that is dependent on the speed of the car, that is what this sounds like.

Here's where it gets bizarre...

This noise only occurs when there is power transfer from the wheels to the clutch, or in reverse. I can go forward all day long and not hear this noise. If I put the trans in reverse there it is again. As an experiment, I got up to 35mph and pushed the clutch pedal in and coasted down the street and you could hear the same noise, threw it in neutral while still coasting, noise went away. Went back home to the garage, back into the garage, and there's the noise. pulled forward, no noise, go back in reverse and it's back again.

I did another experiment. got the engine up to operating temp, did the same 35mph down the street and coasted with the clutch pedal pushed in, noise is gone. Get back to the garage and while in reverse, noise is back.

To fully understand what is going on, read the above, but here are the take aways...

1)temperature dependent
2)always happens in reverse
3)never happens when going forward

A little back story, I started hearing a hollow "clang" noise a few months ago when shifting cold, and it was clearly coming from the bellhousing. Took it to rotary performance and they test drove it and they also heard the noise, but said not to worry about it. Well that noise is gone and has devolved into this new noise.

 

Sounds like a bearing in the trans is getting growly

 

input shaft bearing maybe, it has the most interaction with the clutch. I had the trans rebuild last year, and the only things that got reused where the gears and the transmission case.

If your theory is correct, the bearing is sitting in its good spot going forward, but take a load off of it, or direct power transfer the other way, it gets in its bad spot?

 

My theory: your front differential mount is probably allowing the differential to rotate forward slightly under decel/reversing thus causing the driveshaft to rub on the exhaust heat shield.

 

Input shaft bearing should go away when clutch is pushed in, me thinks.

 

I say if it is speed dependent and not RPM dependant it's on the output side, not the input side.

 

so, broken diff mount?

 

Im seeing some contradicting statements here.
What did you do different between the two experiments?

 

The same exact test, only difference was temperature.

 

It's a truly MPH based noise? Could be a random rattle like the heat shield posted above, or just about anything else that would rattle.

 

I really need to make a video but i dont think it would pick up the noise.

I was slow at work yesterday, so I pulled the car into the shop and jacked the *** end up. I spun the wheels in gear, out of gear, clutch in and out...no noise.

I put the car back on the ground and my coworker held onto the car as i back up (that was funny, as he slid across the floor) and he swears the noise is coming from the drive shaft somewhere in line with the driver seat.

So, it isn't the clutch and somehow the drive shaft is rubbing on something in reverse, or any time power is transmitted from the rear wheels to the transmission.

I slid my coworker across the floor a few times, and he swears whatever is making that noise is in line with the driver seat. We jacked the car up again and slid under, you canty see anything. I think it's going to need to be on a lift. fml.

 

Try rear wheels off..car UP.
check the brake shields?
Those damn things can rub if they get a slight breeze..(can rub too if your security screws on the disc are gone.

 

All those screws do is hold the rotor in place when the wheel is removed, once the wheel is mounted they are redundant.
Don't see how their absence could cause the brake shield to rattle.

 

ya..sorry..didn't elaborate..
They will When you turn the disc with the wheel off and those screws are missing.
In order to find the shield rub it is best to have the disc fully secure with a couple wheel nuts to allow a proper test.
This gives me an thought about the rear wheel bearings too.

 

Front u-joint. Or at least mine was. Had a noise that when it started only happened in reverse. Sounded kinda like those little squealers on some brake pads to warn you when your pads are worn out. Only happened in reverse with the clutch out. Then faintly if coasting in reverse, always worse with clutch engaged. Then progressed to noise going forward sometimes( not always) that sounded kinda like a heat shield rattling or something rubbing the driveshaft. Always worse off throttle during decel. Had my daughter convinced once a bird was stuck under the car cause it sounded like a bird chirping. Sometimes sounded like the shifter rattling. At one point early on I checked all the brakes and jacked up the rear crawled under for a look. Nothing except when I turned the wheels I could get a faint metallic pop from the shaft. Drove it months more figured when something broke I'd know for sure. Finally put a new front U-joint in a previous shaft I had pulled out years ago( rear was fine) and replaced the driveshaft. Front U-joint was locked in one direction and rough in the other. Quite as can be now.

 

Here is a video of the sound mine was making.

 

That is Exactly what mine sounds like in reverse and in decel...damnit, I can't afford this now.

 

Cancel.

 

I used this U-joint to replace the stock staked in one.
Rockford Driveline Speciality Universal Joint :: MotorMaster

There are instructions on here about how to do it. Does involve grinding the staking off so the old ones can be pressed/ hammered out.

Also the part# look up. http://rockforddriveline.com/replacem.htm

 

Dak..if you can elaborate please for those of us that may not know the terminology.
Can you explain "staking"?..is it like a lip on the hole of the driveshaft or the cup of the U joint?.

 

Here's a picture of a staked joint:

 

Staked pretty much means spot welded it seems

 

If you have a press just push the caps through the staking. No need to grind before removal just to clean up afterwards.

 

Staked means to physically deform the bore of the driveshaft into the edge of the universal joint cap.

Another example of "staked" is the rear axle nuts, which are staked into a groove into the axles to prevent them from spinning loose.

 

I don't want to get into a pissing match here but, the caps are hard and the yoke is not. The stakes you see on the u-joint cap is metal from the yoke that has been displaced against the cap to hold it in.