How to know if a transmission is bad

Go somewhere else or rebuild the motor you have . If the tranny was bad they may have changed the fluid in hopes it would fix it , I don't think there's any way to tell short of driving it or removing the pan to look for metal .

If the price is right see if they'll give you some kind of guarantee, in writing. Like 30 days or something. If not, go somewhere else. Hope that helps! Jim

There is now great easy way to tell. As Jim suggested above, try to get a used one with a warranty.