stick newbie so just strickly guessing (kinda bored), either not deep enough or something in the path ain't concentric. makes sense (what was said) if it has been drilled for the pilot bushing & it has cuz it is in there then I'd think #2. Is the final distance it wont go in to seat the same distance as the length of the pilot bushing? If so that tell me that the tip of the input shaft is hitting it off center as opposed to sliding into it dead on