Mine acted the same way.....I deliver our rental equipment , and on a few occasions , got stooped on a steep hill....gravel roads...I would power brake , floor it...and nothing....not even tire spin. I would try 4WD and 2WD and get nothing...
Not sure if the triple disc and VB upgrade did it , the Smarty or both....but now I can brake the tires loose on dry pavement with 14k hooked onto the truck.
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06 3500 SRW MC ,Smarty REVO,X2 Race stack, Commander, Monster Air COI,AFE Torque tube,FASS 150 HPFP LP,Muffler delete,Tipple disc Converter and VB ,ProComp 2" leveling kit,Timbren's,Reese Class V Tow Beast