so you said your having an overcharging problem? that could only be one thing to my knowledge. and that is the voltage regukator in the alternator. I could be wrong but i dont think it would affect the tranny any. if you said it is random then it would be kind of hard to test. but if the problem is steady you could always test the voltage by placing a volt meter on the positive cable on the back of the alternator.it should read around 14.5 volts.