What''s the gear ratio? 240d's are typically geared much lower than 300d' so it's no surprise there's a difference in top speed. Have you checked the linkage by holding the pedal to the floor and having someone check to make sure the linkage is at the stop on the IP?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13