I posted this over on M.Net and I haven't gotten any worthwhile replies (I am of the opinion that M.Net is only good if you are 40+ and want to put those fracking shark teeth in the grill of your miata).

Anyway: My '93 NA6 with about 170k miles on it has begun to make a terrible "clank" when I let the clutch out-- I wasn't worried at first, as the noise would only occur when I let the clutch out quickly, but now it happens even when I ease the clutch out.

In the M.Net archives, people have pointed to the u-joints on the driveshaft as a potential issue. However, I have a feeling that this is something related to the clutch-- but I have no evidence to back this up.

Anyone have some advice they can offer?

 

If you end up pulling the trans for this, have a good look at the bearing support. That is the part where the throwout bearing slides on around the input shaft. Wear there can make the bearing hang and make noise when engaging the clutch. Other than that how about the rubber bumpstop on the clutch pedal where it rides on the switch.

 

Although I am 40, I don't have any shark teeth on my miata.

I had a clanking when the clutch released on my Toyota 4x4. I couldn't duplicate it by hand, went with others advice on the U-joints, (cheapest and easiest of possibilities first). Sure enough, one was toast and the clanking disappeared.

FWIW

 

I would probably check the u-joints for slop before anything else.

 

Does it sound like someone is banging big metal salad forks together? If so, I've had the same issue with two different drive shafts.

 

The sound is more like a pinging (not engine pinging), like a metal rod hitting a flagpole.

I did some investigation today and I am starting to lean toward u-joints on the prop shaft. No one around today that I trusted to release the clutch while I was under the car-- so with my solo effort I could more or less tell it was the prop shaft.
I've got some buddies over tomorrow who can do the clutch while I lie under the car (solidly on jack stands, of course). Will have a better idea then

 

Yep- front u-joint on the propshaft. Just bought a used one on eBay for $25 (29k miles on it). Should suffice.