I am sorry to disagree with Rocky as he usually has it right, but the box is designed to be adjusted. It often needs adjsuting the first time prior to completing 100K miles.

Its probably just a bit too tight. Back your adjustment off an eighth of a turn and see if that doesn't free it up.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.