i know that you need a grounding line on the tranny as well as two or three on the motor. you said you have two tranny's, mix and match to make one. or is 5th gear blown on both tranny's. as far them being weak, i don't think that's the case. i had 225,000 HARD miles on my transmission and when i rebuilt it, it only showed signs of normal wear. but i'm thinking that if you didn't have that ground hooked up, that could be the source of your problem. most people don't realize that engines and transmissions create static electricity and need to be grounded. i have four grounds alone on my engine and two on the transmission. if you need gears you are gonna have to go to the dealership to find them. i looked at new gears for my tranny and it was almost $400.