same car here but one year newer (82), my situation is where I can hear the motors running but no movement front and back, but the reclining motors work fine. I have tried clean the rails and lube them but to no avail. I was able to move it backwards manually using grip pliers, but won't move forward electronically or manually even using grip pliers. Again the reclining motor works but the forward and back on the rails are stuck, I have left the seat in my garage upside down. Any help for us with seating issues especially for our passengers. Tried a search and landed on this one that was close to my situation, unless someone finds a better search results. Thanks.

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1982 Mercedes Benz 300SD Weird Yellow Baby