Mystery scraping sound going uphill

Maintenance/Repairs
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1

My 2003 Ford Ranger started making a scraping noise a couple months ago - just a sort of quick metallic rasp that lasts no more than a second. It doesn’t sound like a grinding noise - it’s definitely a scrape, like if you dragged the edge of a shovel along some pavement. The sound comes from the rear of the truck. For a few weeks it only happened when I was driving uphill and making a sharp right turn at the same time. (My morning commute has one such right-turning hill, so I was hearing the sound every day at the same spot.)

A couple weeks ago, when the roads started getting really really terrible with potholes and frost heaves, the sound suddenly started happening more frequently. That same quick little metallic scrape happens almost any time I go over a big bump, and sometimes it seems to just be happening at random, even when the road isn’t that bad!

What I picture when I hear the noise is that something in the undercarriage is loose, is briefly hitting the ground during sharp turns or jostles, scraping against the pavement and then bouncing back up. I’ve looked under the truck but I don’t see anything that looks loose or dangly. My undercarriage is badly rusted, however, so it’s not hard to imagine that something is swinging around that I just don’t see when stationary. This could also be something in the wheels… but I don’t know what.

Does anyone have any ideas?

2

Maybe brake drag ?
We can assume your truck has rear drum brakes. Components can come out of alignment with all the bumps. The first thing I do when I hear scaping noises where I live is crawl underneath while it’s parked and look for debris or something abviously bent and rubbing. The next thing would be to try to duplicate sound on a lift to identify the cause. Otherwise, others will have some better ideas .

3

My driveway is on a hill. When I have a load of people or stuff in my wife’s van, the muffler tends to scrape the driveway with a similar sound when going uphill. Maybe your muffler or tailpipe is the source of the sound.