I have a '92 250 Ext cab Cummins Turbo 3/4 ton. My rear drums are 12"x2-1/2" and are 8-lug. Can anyone tell me the cylinder "cup" size so I don't have to pull the hub to find out?

Maybe the "bore size" is what I need? I don't know!?!?!?

 

It is probably 3/4" - get the counter guy (or gal) to see what was available for your year. I just recently went through this same thing for a 77 W200 3/4 ton Dana 60 rear - all the years cross from 77 to at least 96 - stock 3/4 ton is 3/4", 1 tons are 15/16", you can put as large as 1-1/4" in them as long as nothing rubs.

One of the upgrade tricks is to put 1-ton cylinders (15/16&quot on a 3/4 ton to help put more braking on the rear. Dodge did this from the factory starting in 99 (I think) so it should work for your year. Good luck.

 

The '99 diesel rear cylinders are the same as the 3500 from the factory. In later years they also went to the same lining width. There should only be one cylinder size for the '99 diesel truck. The '98 and back used a smaller cylinder for the 2500.