Driveshaft noise
 

About a week ago I was leaving for work and when I backed out of my garage I noticed this odd scraping/squealing noise as the car started moving backwards. I stopped, put the car in drive and didn't hear it as I moved forward. In the interests of time I drove to work and had no issues or other odd noises on my drive.

The next day I had a friend stand outside of the vehicle while I reversed to see if he could locate the sound. We found out it was coming from the center of the car, from the area right behind the transmission. My first though was that the heat shielding around the exhaust may have been rubbing on the driveshaft, but it still didn't make sense to me why I was only hearing it in reverse. So the next day I raised the car on a lift and stood underneath while someone else put it in reverse. I heard the noise but still couldn't tell what exactly was making the noise. A few of the more experienced techs in the shop (I work at a Nissan dealership) came over to help me diagnose, and their first though was that the center support bearing was going out. I started doing some research on failing center support bearings for driveshafts and wasn't satisfied with the results I was finding; my issue didn't seem to compare to any of them.

The last few days, I've been able to hear somewhat of a scraping/rattle when I'm in motion moving forward, at any speed, coming from the same general area. So I put the SVX up on the lift again today after work and removed the heat shield around the exhaust so I could really get a good look at everything driveshaft related. Now I can hear that the noise is not coming from the center support bearing at all, but rather the front half of the driveshaft itself; I don't mean the U-joints or where it connects to anything, I mean the actual shaft is making this noise.

I don't know much about the actual construction of driveshafts, or even if the SVX's is different from other subarus so I'm not sure what to suspect is making the noise. Does anyone have ANY ideas? This noise is going to drive me crazy.

Re: Driveshaft noise
 

I bet it's just scraping against a heat shield or something. When under load, the rear diff will tilt slightly. In reverse it tilts in the opposite direction than when in a forward gear. That's probably why you heard it in reverse but not drive.

In addition to the exhaust heat shields, there is another heat shield above the back of the transmission area. Might be that the top of the driveshaft is rubbing against that.

Not sure how to tell whether the support bearing itself it bad, but there is a round rubber mount that supports the bearing itself. If that were to start to go, it might let the driveshaft drop down to rub the exhaust.

Re: Driveshaft noise
 

Well I know for a fact that nothing is coming into contact with the driveshaft. I completely removed the heatshield that is above the exhaust and there's a good inch or so above the driveshaft with nothing for it to touch.

The support bearing is a little worn, the driveshaft doesn't sit exactly centered in the rubber bushing/boot, but I don't believe it's hanging low enough to contact anything. I had it on the lift and inspected all moving parts in both reverse and drive, nothing is touching.

Re: Driveshaft noise
 

I have a rebuilt drive shaft with grease fittings that I grease yearly. Try lubricating moving parts, maybe something is drying out.

Re: Driveshaft noise
 

It is possible that the worn center support bearing has been putting stress on the ujoints and they're failing. The sound from them may be coming through the hollow shaft, like a cone acts like a megaphone.

Re: Driveshaft noise
 

Was there ever a solution to this? Mine has just developed a similar noise that is most certainly a drive component rubbing against something else. No part of the drive shaft is contacting anything that I can see though. Mine is a 5sp swap with the stock driveshaft lengthened 2 inches. One last possibility is that the drive shaft is rubbing on the shroud at the tail of the transmission that it fit inside of. I will have to remove the shaft from the tranny to see if there is evidence of contact there.

Re: Driveshaft noise
 

I had mine on a lift, removed the heat shield, and still heard the noise for about a day. Then it just up and stopped making noise, still that way today. Not sure what to do I've just left it alone and figured I'll look into it more if it comes up again.