New member here I have a 1984 441 mustang with a 4108 Perkins diesel that I am replacing I have the parts manual but can not find a service manual this machine was sitting for several years and motor was locked up I found a good 4108 with low hours from a sailboat I pulled the engine and pump skid together and swapped the motor so far so good but before I reinstall pump and engine skid I have some questions is the chain case fluid the same fluid used by the hydraulic system I believe is type f transmission fluid ? There is no dip stick on the hydraulic fluid fill how much fluid does this machine hold ? The fuel water trap mounted to side wall does it contain a filter element? Mine just has a metal cone inside inside. Cab where key is located there is a thumb sized rubber push button does anyone know the function of this button ?