Grinding noise: drive axle, brakes, other?

03-10-2014, 09:43 PM
I've had a sort of grinding/scraping noise coming from the right rear area of my 2001 Miata that correlates with road speed (not engine speed), and my fuel economy has been diminishing. I thought it was the drive axle, but now that I have it off, I'm not so sure. What do you think?

When I initially troubleshot it, I raised the rear end, took the rear wheels off, and had my brother press the accelerator while I looked and listened. The left hub spun much more than the right, I think. (Memory is fuzzy, 'cause I haven't had time to deal with it for a few months.) I took the right brake caliper off and it didn't seem to change the behavior significantly. I played around with the drive axles manually, and I thought I felt/heard some friction in the right drive axle where it enters the differential.

Fast forward a few months to today, and I finally got around to pulling off the drive axle. It looks fine as far as I can tell--no worn splines or anything, and I'm not feeling anything funny or friction-y in the CV joints. This is the first time I've done this, though, so I'd appreciate more experienced eyes. I know that getting into the CV joints would be a big job, so I don't want to do that unless/until I'm reasonably confident it's necessary. I checked the differential fluid, btw, and it's fine.

So should I revisit the brakes theory? Open up the CV joints? Or could it be something else entirely?

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