Well this probably doesn't apply to you, but the only problem I've ever had of backing up a hill was low tranny fluid was allowing the tranny to slip.

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Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k