What's the "heavy duty brake system?" I see it on Rockauto.

[Hawkrod]

It is not online. You can buy a CD copy but it is what is called a "final issue" and those do not have all of the original data. The problem is that as time went on the original parts were often superceded or if they were obsolete they were sometimes just deleted. In order to really look into it you need several of them from different time frames. The final issue is better than nothing but I use about a dozen different ones to look stuff up sometimes. This is not something the average person would have the time or inclination for. Also note that sometimes the updates alone will kill you, the 1953-1967 Ford car MPC with every single update takes 27 feet of shelf space! Hawkrod

[flyboy2610]

The size of the brake drum is dependent on the GVWR of the truck. My F250 has a GVWR of 7100 pounds. It uses 2-1/2 inch wide drums and shoes, which is the HD braking system. F250's with lower GVWR's got the light duty brakes, which were 2 inch drums and shoes.