and the viscous fluid which is supposed to be sealed in the coupling leaked out and mixed with the gear oil. I dont know if you could blame that on the gear oil though. The mixture of the two fluids would be responsible for reducing the viscosity of the oil and causing the excess shavings on the plug. A split and leaky coupling could just occur from regular wear and tear on a 15 yr old diff. Did the Redline shockproof work great up until this point? quiet? What weight of shockproof did you use? I was thinking about trying royal purple max gear also, but i cant seem to find it around here anywhere.