dr. diff master cylinder

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joshua dewitt

joshua dewitt

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I ordered the dr. diff master cylinder 15/16" with the plate adaptor. stops great for my manual disc/drum set up. the master reservoir is slanted forward and when braking nose dives. the fluid dribbles out the vent cap, has anyone used this set up and ran into this? or is there something else that can be done? I e-mailed the dr. diff comp. awaiting e-mail back.. just putting feelers out....
 
It's not really the vent that's the problem. The OE caps and seals that come with those master cylinders just suck. I asked Cass about the same issue, he recommended new caps and seals. I bought replacement caps and seals and haven't had a problem since.

I used Dorman 42044 caps and Dorman 42081 gaskets.
 
A brake reservoir shouldn't be vented to the atmosphere, since that would let glycol fluid absorb moisture. Is that MC simply the 1980-90's Dodge truck one?
 
BillGrissom said:
A brake reservoir shouldn't be vented to the atmosphere, since that would let glycol fluid absorb moisture. Is that MC simply the 1980-90's Dodge truck one?
Click to expand...

It's not vented. The caps have a bump that kinda makes it looks like they are though, I can see how someone could think that looking at the caps.

Yeah it's the same one as the 90's trucks, plus just about everything else in that year range. They aren't 15/16" from the factory though, Cass sleeves them down (if you request a 15/16" bore) and modifys them to accept the manual push rod without any changes.
 
I have one of each of his MC's. The 1-1/32" came with a large, 'level' sitting reservoir which he later referred to as a truck reservoir. The 15/16" had the smaller, 'tilted' reservoir.

I shimmed the caps on one of them by adding a plastic discs cut from a milk carton between the rubber gasket and cap. It tightened them up and worked fine - that was before I discovered the Dorman option.
 
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