I have a 1980 450 SEL that I'm trying to find out how to disassemble and put new seals/parts in the power steering pump. My mercedes manual only tells how to replace the front shaft seal. I've got the rear pump cover off but that's as far as Ive got. I have a Z-F pump ( aluminum body ) from the 450 SEL which has a lot of movement in the shaft ( it can be moved in and out too much ), and a cast Iron Z-F pump from my other car ( 79 300 SD ) which I think came off of an 80 model 300 SD. are the two pumps interchangeable ? I'm wanting to take the internal parts off the cast iron pump and use them in the aluminum pump. The only difference I can see so far between the two pumps other than the body material is that the front shaft seal sizes are different. I definitely need to know how to dissasmble these things so I can see if the shafts etc. are interchangeable, the cast iron pump seems to be in good shape other than needing new seals. Also the seal replacement kits I see for these units have two large o-rings and I only see one so far on these. The number on the riveted tag from the aluminum pump on the 450 SEL under Type Nr. is 7672900422 and the other ( 300 SD ) pump is 7672900402. Thanks, Rocky

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