I have a 2000 Southwind gasser on a workhorse chassie with antilock brakes. Time to replace the fluid using a . vacume pump. Should I use dot3, dot4 or synthetic fluid? Is there anything special I need to do to address the antilock system?
I would use the fluid recommended by WH which for your coach it is DOT 3. It has worked since 2000 so why change? For the type of driving that you do, it will be fine as long as you buy a name brand quality brake fluid. You don't need to do anything special for a brake flush with anti-lock but keep in mind that any left over fluid is not to be used in your brake system in the future. Once the seal is broken, use it than dispose of the left overs.
I don't know much about this subject but I do know that the DOT 4 Fluids have a higher heat point. Ie. condensation, boiling and etc.
I can't imagine why the 4's would not not be an improvment. All of the newer Gassers call for DOT4 only.