Marc80

I am getting a INTERMITTENT scraping sound on acceleration, especially on a right turn. It is coming from back behind the seats and a hard to tell which side it originates from. There is nothing visibly interfering. I have removed tires and checked all break parts, and wheel balancing weights. The driveshafts all feel tight as do the wheel bearings. Not sure about lube but there is negligible slop. It sounds like something turning and scraping on a plate of metal. Once I get up to speed it goes away. Some times I can goose it and pretty much make it lessen. If I drive like grandma I can get around without the noise. I guess it is helping me get conservatively through my breakin period with a new motor (From AR Racing -very happy). I have done no work in rear but will be doing brakes and parking brakes this weekend. I am hoping that solves it but I have my doubts. ANY ONE HAVE ANY IDEAS?
This is definitely not a grinding or squeeling noise. THANKS for your time.

Marc in Sarasota

:flag

Paul Borowski

Marc, there is many possibilities for this one. When you mentioned turning it might need the rear end lube changed with new GM positraction additive. I've also seen where parking brake shoe hardware rusted and the p-brake shoes were inside the rotor hub flopping around unattached causing grinding noise. A bad or dry u-joint is another possibility. I once had the "caliper pad" pin fall out of my '75 on the left rear caliper and the pads fell slightly and were riding on the hub of the rotor also making a grinding sound.

Armstrong

Ditto on the caliper retaining pin falling out. That happened to me too.

Geoff1340

My 77 has a "scraping" noise also, Van-Steel rebuilt the trailing arms, replaced all u-joints, flushed differential and used posi additive....I just turn up the radio now... :cool:

Avette4me

May not be anything but, when I went through my suspension, I found that one of my rear spring bolts had broken off. This made some noise and I believe contributed (among all of the other old worn out stuff) to the "squirrel" I experienced on a quick take off.

Larry B.

When mine did that, it was due to the side yokes being excessively worn and the half shaft attaching bolts were hitting the diffential housing.

Marc80

Thanks you all! Keep the ideas coming. I will go through all this stuff when I get some time. (Soon-since this really puts a damper on driving enjoyment.) I can't just turn up the radio either. It ranges from fairly quite to quite loud. It usually doesn't last long since it is only related to acceleration and not speed. It seems to be more noticable when accelerating from stop ...and less when accelerating from 30 Mph or so.

Thanks again. I really appreciate your input and time.

Chris O'

Brake pad? My pads scraped my ft rotor considerably on a left hand turn.

Larry B.

I would NOT keep driving it "until you get some time". The results of a broken U-joint, wheel bearing siezure or in the worst case a spindle breaking could be disasterous. A spinning half shaft loose at one end under the car is not good. It will do lot of damage as some have posted the result here. Fix it later or whenever but don't drive it until you find the cause. TRUST ME... :nonod: :nonod: :nono:

Marc80

Thanks you all. I found the problem(s)
Mostly it was the u joints on the half shafts. one was making the noise but two had no needle bearings left. As typical I also found wheel bearings that needed replacing and also excess transmission slop. I am prepping for a trans as well. Lots going on this weekend:

Man is that rear u joint a pain in the butt on the 80. That ranks right up there with the door handles.

Anyway: tasks for this week: rebuild rear brakes and emergency breaks, changed shocks, wheel bearings, transmission and stall converter. I am looking foreward getting this done and getting it into the shop for paint job. This all started on Halloween when a 90 year old deaf guy pulled right out in front of me. Oh well it needed a 425 hp upgrade anyway. :)

Thanks again you guys

StingRay327

I am having the same problem. I believe I have mine narrowed down to the rear end lube needing to be changed. I've done everything else, so that's gotta be it. Thanks!