Wheel cylinder question

[jboomer]

Took my EB for a drive yesterday and could smell smoke when I was done. I guess the rear driver's side wheel cylinder had frozen and kept the brake mostly engaged and got hot.

Today I checked and sure enough the wheel cylinder was frozen. I tried to pick up a couple of new ones (both rear wheels) but hit a snag. What axle comes stock on a '78 EB? I know it's got the 9" rear end, however there are two different cylinders offered. One that says 2900lbs and one that says 3300 lbs. Any idea which is the one I need or where I can find the info?

Thanks!

 

[Viperwolf1]

Any difference would be in the bore diameter of the cylinder. Bring an old one in and compare.

 

[Apogee]

The '78 BB came with a Ford 9" with SET20 tapered roller axle bearings, which correspond to the 3300# weight rating. They also had 11" x 2.25" drums and 15/16" wheel cylinders, the same as the 76-77 EBs and an bunch of other applications between 1949 and 1997.

 

[jboomer]

Thanks! I went ahead bought the 3300# cylinders (all they had in stock) and they fit perfectly. The truck free rolls so much better now. Next issue is to see if there's a way to "turn up" the braking in the rear. The front wheels lock up so much quicker than the rear wheels that I can't help but wonder if I'm getting max effective braking from the back?

 

[Apogee]

Thanks! I went ahead bought the 3300# cylinders (all they had in stock) and they fit perfectly. The truck free rolls so much better now. Next issue is to see if there's a way to "turn up" the braking in the rear. The front wheels lock up so much quicker than the rear wheels that I can't help but wonder if I'm getting max effective braking from the back?

Start by making sure that your rear drums are in good condition and properly adjusted. New shoes really aren't that expensive, so if yours have ever been saturated with gear lube, brake fluid, etc, now's the time to replace them.

Are you running a proportioning valve in the system? If so, what is it? I prefer the adjustable units over the fixed OE style units as they'll allow you to tune your rear brakes specific to your vehicle and it's handling traits. What size calipers are your running up front? Truck or T-bird/LTD? Do you know what pads you're running?

 

[DirtDonk]

Either one of the sizes will fit perfectly. The only difference is in the inner bore, like was mentioned. The outside dimensions are almost always the same between the different models.
And as you found out, if the book or computer is asking you what cylinder you need, it's because both were available. So the only ways to know is either by the info tags on the vehicle or axle (which I'm guessing are not available right now), or by taking the caps off and measuring the bore.
No way to know, from here, what your axle's original donor had.

Luckily though, they had something that would work, and you're back on the road again.
Might even work better than ever!

Paul