Thanks QDub, that's an interesting set up. I don't have front posi on my Jeep and only a couple of Jeep models offer it since it's hard to steer with a conventional posi.. The Nissan ones use fluid to engage the other side so in normal driving it's basically a one wheel drive..
"Viscous LSD units are popular OEM LSD solutions, as they are relatively simple and cheap to produce. They come in many performance Subarus, Nissans, Mazdas, Toyotas, etc. The LSD unit consists of stacks of thin plates with holes or slots, all suspended in a special silicone fluid. They have no clutches to wear out, and locking characteristics can theoretically be changed by varying fluid viscosity. Generally, however, these units are non-serviceable, and require no special maintenance. As the differential spins, the plates shear the fluid up to a point, after which the fluid provides some resistance to shear, allowing 15-25% torque transfer to the other wheel. The downside is that these units don't act like a limited slip until one wheel actually starts slipping (i.e., they don't prevent slippage), which means the VLSD action often kicks in after you've already exited the corner. Compared to the proactive nature of the Torsen LSDs, the VLSDs are reactive units. They do not prevent slippage, they merely sense differences in rotation, not torque. They also don't allow for very much torque transfer, compared to mechanical or clutch-pack LSDs. They do still work well for starting from a dead stop in slippery conditions. It is important to note that VLSDs locking characteristics occur both during acceleration AND braking, as it can't tell the difference between the two, but merely reacts to the rotational speed differences between the two drive wheels. "