Are all rear axles the same ?

[Aaron]

Quick question

Take off calipers, drums 4 stud 3 stud etc
Just a basic beam.
( doesnt matter about bar size)
Are they all the same? Or do they differ?
If so how?

For example
If you remove a 3 stud drum setup, can you fit a 4 stud drum setup to the same beam?

[Nates-VTR]

What I was told is all the arms are interchangeable as in you can take a 1.1 axel, remove the 'swing arms' either side and fit vtr ones which have disks :)