to everyone that has upgraded the tranny did you upgrade the flex plate at the same time or are you still running the stock one? how much power can the stock flex plate handle? I will replace it if I should but if the stock one is good enough then I would rather save the $500 and put it towards something else.

 

I have direct experience with this! Pictures of original and replacement plate in this thread:
https://www.dieseltruckresource.com/...d.php?t=227137
I bought my '01 in non-running condition. The original flex plate had 100,300 mile on it when it failed. 60,000 of those miles were with an ATS trans and triple lock (?) torque converter, being pushed by a motor putting out between 500 and 550 HP.
For a much stronger flex plate without paying aftermarket prices, you can get a flex plate for an '08 6.7. It's a direct bolt in replacement. Even at the Dodge Dealer, it was only $121.00, and if you can get the Cummins part number, it's probably cheaper there. The flex plate for the 6.7 appear to be the same thickness, but there are NO cutouts in it, and it's shot peened to add fatigue resistance.

 

thanks for the info save me couple hundred bucks.