So I was about three quarters of the way through removing the transmission, and decided to jack up the drive wheel to make removing the driveshaft flange bolts easier. Was hand turning the driveshaft and noticed a scraping sound.

Checked around and couldn't find anything; decided to stick my hand up in the tunnel and feel around. BINGO. A small bolt had bounced up and landed in the tunnel under the driveshaft. It was in a spot where it would only occassionally roll and make contact. I tapped on the driveshaft with my wrench and sure enough the sound was the "ping" I had heard intermittently. I guess the tubular construction of the shaft transferred the sound so it was pretty hard to tell exactly where it was coming from. Driveshaft was OK, barely cleaned the rust off one spot.

Investigated the source of the bolt and found it was the one that attaches my alternator adjustment arm to the block. Guess I didn't get it quite tight enough when I swapped engines and it took a couple weeks to work loose. Replaced it with one from the parts stash and snugged everything up.

So I reconnected everything and went for a drive. All normal, sound gone.

Even though I lost a weekend to tracking this down and $45 for the tow I just have to chalk this one up to dumb luck. Dumb because I didn't check to see if I had the bolt tight enough and then the luck of it actually bouncing up into the driveshaft tunnel where it made it sound like something was about to shred itself.

So back to actually improving the car...

Thanks for the suggestions, Brickboard.

-Mario E.
Lawrence, KS