Michael,
Questions about changing over to hydraulic fluid:
1) Do you use Mobil 1 synthetic?
2) Did you just start adding ATF to the hydraulic reservoir or did you flush out system?

I'm thinking of converting. My 91 300E 4matic has about 203k miles. Original transfer case. It started to leak enough around 150 - 175k that I began to use the disable switch in summers. I actually don't enable unless the snow starts to fly. Still works great with the Nokians!

Todd

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07 E350 4Matic wagon, 06 S430 4Matic, 99 SLK 230
retired W210 (x3), W124, W126