1966 F750 Rear Wheel Cylinder Offsets
 

Maybe I'm working on this old truck too late in the evening and had a brain fart. I ordered all new wheel cylinders from NAPA, they list different upper and lowers for the rear but it looks like only the bore sizes are slightly different. The backing plate holes are about centered between the shoe slots for the rods, but the wheel cylinders all have an offset. When assembled (the only way they can go) this leaves one piston way out near the end of the bore and the other in about 1/3. The short side on the upper matches up with a long side on the lower, as if only one piston in each cylinder will be doing the work. That just does not look right. Anyone familiar with this and have a thought? I don't want to lift those hubs & drums on and off any more times than is absolutely necessary. I can't count on what was in there when I got the truck being the correct parts. Thanks very much.

What size are the rear brake shoes?

Thanks for looking - They are 15 x 5 rear shoes. I took it apart again and measured everything to make sure that the piston that is getting pushed 3/8" deeper into the wheel cylinder was not actually in far enough to block the port, and the ports are left clear. Looking at the old cylinder bore staining I see that one piston resided near the outer end of the cylinder bore and the other was set back, I guess that is just they way it goes together. I had grabbed another Dayton hub 2-speed rear from salvage for spare parts and that Ford was probably 70s and the wheel cylinder ports were centered but have a different bolt spread.


One other thing I didn't see in my manual was the hose layout for the booster under the cab - that takes direct manifold vacuum correct? I found the vent cap that goes in the cab from another truck. I'll post a photo of this project when it stops raining.