[Zeke]

Being around engines somewhat when something is different because it's bolted up or not bolted up, I'd be looking at that from a simple logic and deduction POV. So what do I know about those engines? Nuffin.

However, I would take the tranny to the shop or install the engine back in the car and run it on a lift. I learned the hard way that when running a car on a lift sometimes the suspension has to be loaded. Long story on that. So maybe the best would be a chassis dyno.

What do I suspect? Well, anything that can potentially move when a stress is applied. Let's just say for grins that the trans or suspension opens a crack in the block where there is an oil passage.

Only thinking with a keyboard, nothing else.