A 67
Caravel would use a 3500 pound Henschen axle, with 10 inch brakes. Rarely do we supply one with 12 inch brakes.
It will not work on your 68 30 foot Airstream since it has 10 minch brakes and your 30 footer requires 12 inch brakes.
Both axles must be the same rating and have the same operational qualities.
It's not likely that the axle in question is bad, but it could be.
If you can provide his name via a PM, I will look up the records to find out that axles age.
Andy