I need to replace differential of of my 1977 240-D 123 series because of the noise. The ones that are available with the old parts dealers have differentials of the following "ratio" and I am not sure which one would be the best. Help would be highly appreciated.

(a) 3.69 (b) 3.92 and (c) 3.48


I am told by some one that if the ratio is higher (eg 3.92) it is better then when the ratio is lower (eg 3.48). Please comment on this too.

Regards