It would be a good idea to check your tranny fluid every time you use it until you are dead certain it's not leaking anymore. I had a brand new ZF tranny that had just seen its first fluid change at around 40 hours of run time. After the change, all the new fluid leaked out the drain plug unnoticed and the tranny seized, ruining the unit & necessitating another replacement. The drain plug was tight enough to need a wrench to open it, and the washer was intact and free of marring or deformation. Its seat in the tranny was not deformed, and there was no cross threading. The mechanics I spoke to said that if even if the plug wasn't torqued to exact specs, if it required a wrench to loosen it then it should never have leaked. But leak it did, and had I been checking it every time until it proved it was holding its fluid, I would have saved myself a lot of work and nearly $2000.
Dan Morehouse
1981 E-38 'Next Exit"