Just bought a T56 out of a 95 Z28 on Ebay.

The guy claimed it shifted fine and there is nothing wrong with it. Is there any way to bench test this thing?

It shifts into all 7 gears pretty smooth and without much effort, but of course there is no load on it.

I know I've taken a gamble but would still like to discover any problems before installing it.

 

Not much to test, but you can try putting the trans in each gear, and hold the outputshaft while trying to turn the inputshaft. Put some cheap fluid in and tip it forward to make sure the input seal doesn't leak. Put a new output/yoke seal on it regardless. It's tough to test the input bearing, but you can wiggle the input shaft to see how much end-play it has.. A stock unit can have alot of wiggle and still function well. If it was rebuilt better-than-stock, it should hopefully have less wiggle..