rear disc brakes on 8 3/4
Sigh. Ok-
1. Small bolt pattern axles can only be used with small bolt pattern brakes. That's it. Even if you re-drill the stock axles to BBP, you still have to use SBP backing plates and SBP drums and re-drill them as well. The axle flange offset is unique to the A-body SBP axles, nothing else from the factory has that offset.
2. Big bolt pattern brakes can only be used with big bolt pattern axles. That means you can not use big bolt pattern rear drums and backing plates (10x2.5, 11x2, 11x2.5, or 11x3) with ANY stock A-body 8 3/4 axle, as they were all SBP from the factory.
You can't re-drill SBP drums to BBP and use them with regular BBP axles, the drums will not line up with the shoes. Re-drilled SBP drums must be used with re-drilled SBP axles.
If you have *most* aftermarket BBP axles, you must use BBP brakes. Not re-drilled SBP brakes, but brakes that were originally used with BBP axles. There are some aftermarket BBP axles that were available with the SBP axle flange offset, but those can only be used with re-drilled SBP brakes.
That's why it's important for the disk conversion. The bolt pattern itself isn't the problem, you can drill any pattern you want. It's the offset of the axle flange that matters, and BBP axles and SBP axles had different axle flange offsets from the factory. For the disk conversion, the caliper must be centered over the rotor. The rotor will be in a different place with a BBP axle compared to a SBP axle, so you must use a kit that was intended for your axle flange offset. Sounds like Dr. Diff makes kits for either style, but you have to know what you have. A redrilled SBP axle is not the same as a BBP axle, even if the bolt pattern was changed to be the same.
This is the problem...
Sigh. Ok-
1. Small bolt pattern axles can only be used with small bolt pattern brakes. That's it. Even if you re-drill the stock axles to BBP, you still have to use SBP backing plates and SBP drums and re-drill them as well. The axle flange offset is unique to the A-body SBP axles, nothing else from the factory has that offset.
2. Big bolt pattern brakes can only be used with big bolt pattern axles. That means you can not use big bolt pattern rear drums and backing plates (10x2.5, 11x2, 11x2.5, or 11x3) with ANY stock A-body 8 3/4 axle, as they were all SBP from the factory.
You can't re-drill SBP drums to BBP and use them with regular BBP axles, the drums will not line up with the shoes. Re-drilled SBP drums must be used with re-drilled SBP axles.
If you have *most* aftermarket BBP axles, you must use BBP brakes. Not re-drilled SBP brakes, but brakes that were originally used with BBP axles. There are some aftermarket BBP axles that were available with the SBP axle flange offset, but those can only be used with re-drilled SBP brakes.
That's why it's important for the disk conversion. The bolt pattern itself isn't the problem, you can drill any pattern you want. It's the offset of the axle flange that matters, and BBP axles and SBP axles had different axle flange offsets from the factory. For the disk conversion, the caliper must be centered over the rotor. The rotor will be in a different place with a BBP axle compared to a SBP axle, so you must use a kit that was intended for your axle flange offset. Sounds like Dr. Diff makes kits for either style, but you have to know what you have. A redrilled SBP axle is not the same as a BBP axle, even if the bolt pattern was changed to be the same.
This is the problem...