Since this is an old g-wagen the tranny has a short drive shaft that goes to the transfer case. All looks good there. Through a little research this morning I am leaning toward the pressure modulator valve on the side of the transmission. Since it is slipping in all gears it makes sense that it would be the problem.
Thoughts?
M

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91 300GD SWB with transplanted 87 OM603 turbo motor