I have a 95 subaru with 202K mj. When coming to a stop, I get a clunk from the back at about 10 mpg. It happens almost all the time whether braking from 50 or 20 mph. It sounds like a wrench sliding against a part of the metal frame, but of course it's not.

 

I'm thinking something about the rear differential or the knuckle joint. I just thought that this is so distinctive that someone would recognize it.

that's near the point in time when some weight/force from 'nosedive' might be vectored back onto the rear suspension so, I'm wondering if bouncing the car up and down in the rear might duplicate the problem?

 

does seem like a bushing or something similar

Does it have drums or is it a LX? Ive seen the same problem on some cars with rear drums. I think something inside the drum was bent. Id take the drums off and inspect the components. Compare left to right.

Well I think that I mostly solved the problem. The rear differential was only 1/2 full. I added 12 oz to bring it up to the overflow [i couldn't get the drain plug out so that's the best that I could do].

 

I think that the rear differential was free wheeling and as I braked, it caused a thud when the knuckle reversed as the drive shaft stopped. The knuckle is a little loose and rotates about 3/8" as measured on the perifery when moved back and forth by hand. With the addition gear oil in the differential, it is damped and doesn't free wheel.

The rear differential free wheels most of the time anyway since the majority of driving load is placed on the front axles and differential.

 

Play at the knuckle is likely a bad wheel bearing. If it has noticeable play the bearing is about to fail entirely and you will be left with a crooked wheel at the least. You need to investigate further and find the exact source of the play.

any play in that wheel could cause noise in the rear end, I'd be very conscerned about any side to side play in the wheel. Is it left to right or up and down?

Maybe it is a worn strut top