I am looking at a Pac Brake, but what all do I need for it to be used with an Auto?
Do I need the Co-poilt?
How hard is is going to be on the Stock Tranny?

 

I believe the '05 and earlier have to have some sort of tranny controller, such as the Co-Pilot you mentioned.

My guess is the exhaust brake is better for the tranny because it seems to act like the tranny is in tow/haul mode but shift points are normal. Do you follow? I'm betting you get higher line pressures in the tranny also. But this is all speculation.