[Tf175]

Thanks to your input I have located two air tanks , rear one has an automatic drain , front has a drain cock. Looking closer at the frame member tanks , I now see the air brake lines are coming to manifolds (?) , not going into the rectangular tank . It looks like the auto drain on rear tank is working as the outlet is clean .
I was thinking about a more modern air dryer , will look into that later on .
Two air bags per wheel at the rear , apparently.
Your help is greatly appreciated. I hope I can be of some help to you all in the future.
Chris