My 1971 280SL W113 has the standard 4.08 gear..no problems and it sounds like a roadster should at speed !!!
The last of the 280SL production run did have a 3.92 gear,

Ed A.

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http://i19.photobucket.com/albums/b1...c/GOWIDE-1.jpg
1971 280SL ROADSTER
1988 300CE TWIN TURBO WIDEBODY
1994 E320 CABRIOLET
1999 C43 AMG
2005 G55K AMG
2008 CLK63 AMG BLACK SERIES