75 Mack

I have a 75 f model Mack that will not build pressure. When I started looking around I found a valve under the cab at the brake pedal that was leaking air and oil. Can I just replace it or is the oil a sign of a bigger problem? Also I keep reading about air dryers on brake systems but I have not been able to find one. Are they on the older trucks?

I have done that with my 7.3 before. I guess I just need a 40 acre lot lot to learn the truck. Thanks for the help. 

As I said I’m new to big trucks. I have a 7.3 6 speed but shifting gears in the Mack is a LOT different. Do y’all have any pointers. I do good in reverse but you have to go forward sometime. 

I know they replaced the passenger side a few years ago. I noticed today that there are 2 chips in the driver side. 

I have more pics just having trouble uploading them. I’ll get more up soon. It is a 1975 f model. When it comes to getting parts for these trucks how hard are they to find? 

I will try to get some better pics. It’s a f785st which from the little research I’ve done has the 675 engine with 237 HP. They added the bed and ramps to pull the dozer onto the truck. 

Hi I’m new to Mack trucks. Recently acquired one that was my wife’s grandpas that he used to haul a dozer. Just wanting to learn what I can.