I'm getting a shudder just before the shift point on my 4R70W in 2nd & 3rd. I am starting to feel slip. Any fixes? How hard is it to rebuild a trannie with average skill levels? I can drop it and put it in but have never rebuit a trans. There is seal leakage in the front and I have an fluid overfill situation. I just bought it ('94 Bird) and the last person to add fluid way overfilled it. Thanks for any help you can give me.