I have an '81 F100 with the Small BP 9" (5 on 4.5"), after doing some thinking (very dangerous) could i bolt Exploer rear disc brakes on my axle tubes without modification? The calipers are held with the backing plates which bolt to the axle housing. and i could use the discs from the explorer also, same bolt pattern. I guess what i really need to know is, are the 8.8 flange bolt pattern and the small pattern 9" flange the same bolt pattern?

 

This is something you'll have to investigate. I know the 5x5.5 9" and 8.8 of this era share the same bolt pattern and backing plate for the drums, no clue on the Explorer stuff though.

 

i looked when i got home it looks like the flange is the same as the big bearing 9", I found a website with a pic of both.

 

google! there is a ton of info about this. infact ford (or somebody) sells this as a conversion kit using stock exploder parts. and from what i read a lot of it has to do with if its a big bearing rear end or not