The inching valve could be stuck/sticking from gunk....or the piston cup in the valve is worn and hanging up...is a simple device really,just a single brake line going to a valve with a piston and cup the push down on a pin in the transmission to put it in neutral...it can be accessed fairly easily from the wheel well on the leftmside...should take a 7/8 wrench to unscrew it out of then trans...lcan rebuild them with regular brake piston cups that youncan get at NAPA or any other quality auto parts store...