My Nismo GT Pro 2 way is very clunky at low speeds ie 5kms or less. Its currently set to the softest setting, and yes its damn clunky when the clutch is out. You either have to get used to it, or get rid of it.
I put fresh redline oil in my diff when i got it (it was just run in when i put it in my car.) It has about 5000 kms on it, and its always clunky, but damn good for corner speed (hooks up way better than std), and locking the rears if i need it (take off, and compression lockups)