I have the axles that were in my Dad's 1991 W250 Cummins with the 3-speed Automatic.... what ratio are the axles most likely?

 

3.07

 

Look on the case for a D61 on the front axle, and D71 on the rear axle. The 3.07 diffs were a special animal....so they had special cases.

But more then likely they are 3.07 diffs if the truck was non-IC and equipped with a regular 3 speed auto tranny.

 

My dad's same set up has 3.07 Dana 71/61s