Join Date: Jun 2005
Location: ID, MT, ND, I'm a transient
Car: 2004 Outback Wagon, Mystic Blue Pearl
Feedback Score: 0 reviews
The action of the rear diff that you describe, where it doesn't "diff out" as easily when new, is news to me. There is nothing in an open differential to maintain traction to both wheels, so there is no reason for that to change. "Diffing out" as you call has everything to do with your traction to the surface you are on, and nothing else. Only way to help that his with new tires or weight distribution. . .that sort of thing.
What you described is more typical with a VLSDs they put in these cars from 2000 up. The VLSD works fairly well when it is new, but as the fluid is overheated it becomes less and less effective. Viscous couplings rely on a silicone fluid that changes viscosity with temperature, so that when the plates in the coupling are not turning at the same rate, the fluid becomes more viscous and helps to transfer power. The gear oil that is used in the rear differential on an LSD is for lubrication only, and has no interaction with the silicone fluid and viscous discs.
It sounds to me more like you are not getting the amount of torque transfer to the rear end that you would like, which would imply issues with the center differential, not the rear. So it seems like that is where you focus should be, along with getting a set of tires that are going to give you better traction on the two wheels that are getting power.
I'm not retarded, I just don't proofread my posts