Well i don't know if anyone else has done this but on my 350 when I installed new bearings in the front diff i installed the clutch pack springs backwards. I'm yet to see only one wheel spin. Both wheels pull and the front tires are wearing as a result of it i'm sure. Thinking about doing this to the front diff on the 400. Also having good brakes on the front helps. Applying the front brakes causes both wheels to pull so i'm told. Other than that you'd have to get a DGL.