looking for replace part for old rockwell axle the

I have a old dump truck that has had lots of parts swapped before i brought it.

Pretty sure it has older rockwell axles 70-80 year ish 2 axles in a 1970 dump truck.
The front Axle has a power divider on the upper right side. passenger side has one line running to it and small round brake can almost looking part on it. That has rubber on inside that fills with air and pushes on flat metal plate attached to a rod going inside the rear. only part number i could find (234433).

It leaks air...

looking for replace part for old rockwell axle the

looking for replace part for old rockwell axle the