Power brake booster failure ?

[Highbanked Hauler]

 I am doing the disc brake upgrade on my sled and can only get some pressure at the calipers.  I have bled this thing to death with clear fluid coming out and have even changed the master cylinder. This thing is off of a 68 and I am guessing it was original to that car.  When a booster fails what are the signs ?

[LaOtto70Charger]

Mine last year had very little brake force even with two feet on the pedal.  Including when checking at the caliper with a pressure gauge.  I switched it to manual until I got a new dual diaphragm booster to put in since I was still running the drum booster.  Which I still need to do this year.

[303 Mopar]

Make sure you have the right booster.  An original power brake booster for drums will NOT work. 

Original drum booster on the left, correct disc-drum booster on the right.

[Highbanked Hauler]

Make sure you have the right booster.  An original power brake booster for drums will NOT work. 

Original drum booster on the left, correct disc-drum booster on the right.

   Thanks, mine is the one on the left for drum brakes.  I took the booster out and put a disc/drum master cyl. from another car,put the original push rod in and got some pressure but not a lot and bled everything again. I have a new aluminum master cyl. bench bled which didn't work with the old booster and I haven't tried it  as manual yet.

[303 Mopar]

   Thanks, mine is the one on the left for drum brakes.  I took the booster out and put a disc/drum master cyl. from another car,put the original push rod in and got some pressure but not a lot and bled everything again. I have a new aluminum master cyl. bench bled which didn't work with the old booster and I haven't tried it  as manual yet.

You will need the new booster.  Also, you will need to enlarge the hole in the firewall about an 3/4".

http://www.doctordiff.com/bendix-style-dual-diaphragm-booster.html

[Highbanked Hauler]

 The aluminum master cylinder  that I have is a Dr Diff  unit which is headed for a manual disc Challenger. Other than an adjustable push rod the same master should work in a Charger without a booster shouldn't it ?
     Do you know the reason a drum brake master won't work with a disc brake system ?

[303 Mopar]

The aluminum master cylinder  that I have is a Dr Diff  unit which is headed for a manual disc Challenger. Other than an adjustable push rod the same master should work in a Charger without a booster shouldn't it ?
     Do you know the reason a drum brake master won't work with a disc brake system ?

I have not switched from power to manual so I would call Cass at Dr Diff and he can help you. 

The disc-drum master has a larger res in the rear (which is actually for the front discs).  The discs require more pressure and fluid than drums.

[Highbanked Hauler]

 I am going to see if I can get by with manual discs like the Challenger has. It can be put in later if needed.

[c00nhunterjoe]

I know the leverage on the pedal is different from power to manual. As long as you swap pedals and all, the swap should be fine.

[Bronzedodge]

I'll second what 303 said about the boosters.  My car was original power drum, swapped to A-body disc.  Did not "feel" right w/ the drum booster.  Swapped in a original disc booster.  Much improved.  As far as pedal linkage, power linkage is same drum to disc, same for manual I believe.  I spoke to "The Ramm Man" at Carlisle, he said the same thing.

Later, the booster failed - symptom was a hard pedal and sound of vacuum leak when on the pedal.  Booster Dewey in Oregon fixed it.