Spindle diff. between disc and drum brakes?

[ChadGiles70]

I have a 70 blazer that I'm converting to disc brakes using an axle out of a late 70's truck. I'm having issues with the inner brake pads not fitting between the dust plate and the rotor for one. Also, the caliper on the driver side is hitting the steering arm! Any thoughts from you guys? But I was noticing in other threads that people were talking about the spindles being changed as well, What are the differences between them to make it that you have to change them? I got a little frustrated last night so any help will be great!

[69TowRig]

I swapped mine over to power discs from an '84 with a corporate 10-bolt.

You will have to run the disc knuckles because the hole pattern is clocked differently. That is to say that the six holes are rotated so that the caliper mounts are positioned away from all the interfering parts. The disc knuckles are also notched in the casting to clear the calipers.

The 10-bolt I used had big-bearing spindles so there were a couple differences there too, but if I recall correctly the hub mounting surface is positioned 1/4" further away from the knuckle on the disc spindles. Net effect is that the disc-brake trucks have stub shafts that are longer, so you will need either the complete Dana axle shaft assemblies (inner and outer) or you will have to use a fine-thread 7/16-20 bolt and a fender washer to retain the axle shaft in the locking hub assemby when you put it together. You cannot simply swap stub shafts because the 69-72 trucks run smaller axle u-joints than the 73-79 stuff. 80-88 is 19-spline on the 10-bolt inners and those do not swap. I think the 89-91 stuff does (30-spline inners).

I used to remember more about what is different but it has been about 4 years since I did this swap so I do not remember all the particulars anymore. I will search around I know I posted up some details years ago to another person.