Hello, I have a recently purchased 03 silverado 2500hd that I bought as a plow truck. I noticed that the input shaft seal was leaking so I removed the gearbox, removed the locking ring and unscrewed the “cap” out of the housing. I replaced the o ring and shaft seal but it doesn’t seem like I am able to seat the shaft assembly back in the housing far enough to screw the cap back in enough. Am I missing something? Greg