Does stock brake system use DOT3 fluid? I was wondering if there would be benefit to switch to DOT4.

 

Dot 3 is called for.
Personally I see no advantage to 4 as long as you change fluid every couple of years.

 

what about higher boiling point of DOT4?

 

Are you racing? How hot does your fluid get? If you want "upgrade" go ahead it is your truck.

 

I thought the switch from DOT3 to another type of fluid required the replacement of some of the rubber components.

 

Good point! DOT 3 fluids are usually glycol ether based;however, DOT 4 fluids are also glycol ether based, but have a measure of borate esters blended in order to increase the dry and wet boiling points. The DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically once the fluid actually begins to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3 fluid.

Given that the 01 was designed for Dot 3 ,you should make every attempt to stick with that fluid! For example,the internal components of the system were specifically designed and tested for compatibility with DOT 3. Because DOT 4 fluids contain a different chemical composition, the system and components may not necessarily react in a positive fashion to the borate esters floating around in the mix.