[Caprimaniac]

Appears there’s nothing wrong with the engine. Did you check all the drivetrain-bits? Diff, axles and gearbox?

i remember the thread where you posted some pics of the car. Hopefully get it together & running again.

 

[289_Don]

Yeah, you're going to have to do more than pull the pan. Pull some rod caps. Pull a main cap or two. Look for rods that are darker than the rest, that would be a good indication of a spun bearing. Nobody can just look at the outside of an engine and be like "ah ha!" and tell you what's wrong. Just because it's not locked up doesn't mean there aren't any rod bearings that are FUBAR. I've taken apart plenty of engines with spun bearings that would still turn with a wrench.

Unless it has a big obvious hole in the block! But I don’t see one...

 

[Enjoy_the_Ride]

a differential could go kaboom klunk

 

[cntinuum]

Reading thru this thread reminded me a a similar issue I had with my 1970 AMX. I was driving on a freeway in LA when a load noise started coming from the engine. Coasted off the road and had the car towed to my mechanic in Glendale. He tore the engine down and found metal slugs lodged into the top of some of the pistons. They looked like the knockouts from an electrical panel. I guess I must have made someone upset and they dumped this in the carb. Ended up replacing the pistons and finding out the original pistons were low compression. What a difference having the high compression pistons in the engine. You will only know what the cause of the problem is when you tear it apart until you find it.

 

[JV106]

I have heard failing smog pumps sound like a spun bearing.
you will likely never figure it out from after all these years.

Yeah they do. That happened to me when I was a kid. It shut the motor down and all. I remember someone told me to take the belt off and see if it start up. Sure enough it did. I forgot all about that until you posted this.