PSA: Change the oil in the tcase every 30k miles. Clutchpack material in the fluid (what little of it there is) and the deterioration of the friction modifier makes the car bind and make tons of noise. Change the fluid and I would bet your car will return to smooth and quiet.
I had a bad transfer case in my car, when I pulled into work the car came to an abrupt hault and required substantial throttle to even creep forward. I had a 30k mile transfer case out of a 328xi that I got on ebay and had it put in and the car feels great. I personally believe that the chains in these transfer cases slack over time and with hard driving as the new tcase has taken a substantial amount of drivetrain 'clunk' out of experience.
| PROcede Rev3 | Vishnu Meth | DCI | BMW Perf. Exhaust | AR Coated/Catless | CP-E FMIC | Quaife |