I lost reverse on my 79 300D at one point during my ownership, it would only barely work on level ground. I tried to get at the bolt to adjust the band but couldn't, so I took it to a local mercedes specialist. The charged me $50 to adjust the band for me. After that reverse worked perfectly, nice and strong. Might be worth spending the $50….

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold