64 F350
I bought NAPA front brake shoes which have one shoe with longer friction material which I understand to be the rear/secondary shoe. When I got home I see that the shoes on the truck look to be equal lengths. Mine is a uniservo brake and the illustration in the original manual seems to jive that the rear brake should have a longer liner. Ive done a little searching and I think I get the general principal of the primary/secondary arrangement.

Manual shows a duo-servo brake also and shoes look to be the same length. Were uni- and duo-servo front brakes both available on the truck? Maybe someone put the wrong shoes on. Anyone shed any light/advice on my situation?

Also, makes me wonder about the rear which is a duo-servo type but has a longer/shorter arrangement. At least the shoes that went on look just like the ones that came off AND look like the pic in the book.

 

I have seen many relined brakes that had equal length material on all shoes. That may be the case here in question. Do the shoes float with a adjustable star wheel on bottom or a fixed location adjusting each seperately?

 

They have star wheel on bottom.

Just to be clear, my new shoes from NAPA have long/short. The old shoes coming off truck are equal length. Im waiting on taking my cores back til I make sure I have the right thing.

 

Are you sure that someone didn't put both short shoes on one side and both long shoes on the other? That's how my truck came from the PO.

 

I had the same thing as Old Crow when I bought my truck a month or so ago. All of the secondary's were on the left side and primary's were on the right from the PO.

 

Installing the same shoes on each side is a very common occurance, especially with people that dont do much brake repair. I have seen mechanics that constantly remind others they are "certified technicians" do the same thing over and over again. In the less recent years, when most of the replacement parts were still made in this country, and when drum brakes were the mainstream, lining materials came in a wide range of different grades and colors. The primary shoes were usually a light tan color and the secondaries were gray. The primaries were also noticably harder than secondaries.

It was actually common practice, before there was such a diverse range of vehicles, that Guber at your local Wally's Garage, would reline the shoes in house, usually by riveting. Then would grind the arc on linings to perfectly match diameter of newly machined drums. Later years gave way to purchasing relined shoes that were already prearc'ed close to the maximum allowed diameter of given drums.

 

Good thoughts but I just checked. The shoes are all the same. Obviously I am not very familiar with drum brakes either.

I'm going to proceed with installing the ones with shorter lining toward the front of truck and the longer on the rear unless someone hear suggests otherwise.

I am still curious....would anyone know if two different front brakes were available? There are illustrations in the manual side by side of a single servo and dual servo. The shoes on the dual look identical but the ones on the single obviously show differing lining lengths.

 

Answering myself....just doing some internet parts searching. Looks like the F250 4WD did have a dual servos. The F250 and 350 are in the same section in the manual which would explain the side by side pics.

 

equal length does exist, but as said primary is shorter and towards the front and the secondary is the longest towards the rear.

 

Duo-servo(Bendix) brakes are nothing more than the shoes become self energizing in forward or reverse rotation when engaged. There are some very complicated variations of this design. They became the standard used by all major US car makes by the sixties. Tho Chrysler was still using some extremely strange brake designs during that time.