Dirty Engine/Trans means overhaul?

[NO_H2O]

As far as checking the trans without driving it, select each gear and turn the input shaft to see that the output flanges turn and that there is not alot of slop(backlash) in each gear and that it shifts smooth and positive. If the car is up on jack-stands it will make it eazy. A few seals can be changed with the trans insalled. Even with all this checked and no trouble found, it can still not check good when you drive it but you might catch something before you insall the engine.