I have had similar issues where I thought some major mechancial catastrophy just occurred, only to find out later it was something simple. My most recent experience happened on the way to Fiat Freak Out, and in a twist of irony, Alvon and Mike Bouse (along with Dave Voss who helped me do the repair) helped figure out my issue as well! On the way to the event, my rear diff started sounding like a garbage disposer with marbles in it every time I took my foot off the gas. I thought for sure my rear end had given up the ghost! The last thing I had done was replace my pinion seal. Sure enough, I hadn't properly staked the pinion nut after tightening it, and it had worked its way loose. After retigtening the nut and properly staking it, the car has run fine since.
So congratulations. I know from experience what a relief it is to find out that your mechanical melt down is actually something really simple

John
'82 Fiat Spider Turbo
'56 Abarth 750 GT Corsa MM
'59 Lancia Appia GTE Zagato
'62 Lancia Flaminia 2.5 3C Convertible
'68 Lancia Fulvia Sport Zagato
'70 Moretti Sportiva S2
'12 Abarth 500
'59 MV Agusta 250 Raid
Pictures of my baby!