Is there a way to test a used transmission before install?

[clarkster75]

Short of puting it in the car and installing it, is there a way you can test a transmission, especially one that has been sitting for a long time, to see if its usable?
What about going to the lengths of taking it apart to see the condition of the interior gears? I know that would help if you could see some of the wear on the teeth, and ring/pinion.
I know this is territory best left to a specialty shop, and in most cases its probably better to just by a new one since rebuilds aren't totally expensive relative to the amt of labor it takes to r/r one in/out of a car.
Mainly I an curious to know if the one in my car is salvageable. Ive never had it on the road since I bought it and brought it home.
PS Thx in advance

[Bruce]

The only definitive test is to install it.
There are checks, but passing all the checks does not ensure the gearbox is good.
You can drain the oil. Big chunks means bad news.
Open up the filler plug. You can see the OD of the 1-2 slider with the straight cut reverse gear. If that gear is good, reverse MAY be good.
Run through the gears while turning the input shaft clockwise.
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