No rear brakes. Axle swap..

[vegasanthony]

So here is what I have .
I am rebuilding a 73 swinger disk front 10x2 drum brakes rear dana 60. . On the brakes it pumps away like air in the system. All the way down then back up..now the fronts work great..but the back won't engage barely any.
So on the rear the dana 60 has toyota backing plates as well as drums.(10×2)
The original car had these 15/16

.


The new axle has these 11/16

.

I am wondering if the difference in size would make this porportioning valve no good..
Would the smaller borewheel cylinder require a bigger mastercylinder?
Or would a porportioning valve be the answer

 

[SGBARRACUDA]

I've got to ask, why Toyota backing plates and drums? This opens up a lot of questions. Are the pins long enough, the ones in the wheel cylinder? Shoes adjusted up where they should be?

 

[Dana67Dart]

If you pull the rear drum and measure the distance horizontally from shoe outside to shoe outside what distance do you get?

Now measure the I'd of the drum. Are they almost the same?

Where I'm going is adjustment might be your issue.

Also does your master cyl have residual pressure valve.

Are the front brakes hooked to the rearmost port, and the rear brakes to the front most port of the MC?

 

[vegasanthony]

If you pull the rear drum and measure the distance horizontally from shoe outside to shoe outside what distance do you get?

Now measure the I'd of the drum. Are they almost the same?

Where I'm going is adjustment might be your issue.

Also does your master cyl have residual pressure valve.

Are the front brakes hooked to the rearmost port, and the rear brakes to the front most port of the MC?

I will pull and measure .I did adjust them correctly adjusted to slight drag..
No sure on the residual pressure valve.? What is that

I've got to ask, why Toyota backing plates and drums? This opens up a lot of questions. Are the pins long enough, the ones in the wheel cylinder? Shoes adjusted up where they should be

PO got a narrowed dana 60-Chevy 6 lug..I'm guessing the original ends cut off...1980 toyota has a 6 lug drum 10×2..ect..but with smaller wheel cylinders I gather
Narrow and respline axles..

 

[Dana67Dart]

No sure on the residual pressure valve.? What is that

Typically, drum brakes need to keep a small amount of pressure in the system. A stock 73 master cyl should have a valve built into the front most port. If the MC is not stock it might not have one.

Don't know how typical Toyota brakes are, personally I would dump them and get as much stock parts as you can. Much less headache

 

[Dana67Dart]

Have you checked the adjusters for correct side? If hey we're on the wrong side they might loosen rather than tighten

 

[vegasanthony]

Are the front brakes hooked to the rearmost port, and the rear brakes to the front most port of the MC?

Yes is that right?

 

[SGBARRACUDA]

The small reservoir is the rear brakes.

 

[vegasanthony]

The small reservoir is the rear brakes.

So I have it right..
So I measured everything all is ok.
So I bled the brakes again..
They do get stiff and a decent stiffness..
With the drum of one side it takes twofull pumps to get the wheel cylinder to expand sufficiently to engage the rear pads..
So I button up the rear drums adjust till slight drag...
The second the vacuum from the engine is applied the pedal is really soft and it takes 4 or 5 pumps to build pressure to engage the rear drums..

Help

 

[vegasanthony]

Question..
Would a bad porportioning block cause this? Throwing parts at it probably not the answer..
Already..
New soft lines
New calipers . pads
Master cylinder
Both rear wheel cylinder
I had leaks on install now leak free
Old
Drums and shoes(both within spec)
Booster(obviously works)
Porportioning valve