I recently had a leaky PS box on my W126 and pulled it out. Replaced all the seals per the factory manual EXCEPT that one (the one on the top, steering input shaft seal). I then re-installed the gearbox. Now somehow replacing all the other seals made the leak at the shaft even bigger. In the coming days I will be removing the gearbox once again and replacing the input shaft seal.

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280