Power Drum Brake Questions

[goodemj]

Looking for some brake booster knowledge. I'll start off with my setup and then ask my questions. I have 1969 C-10 lwb 4x4 that currently has drum/drum power brakes. My mc is leaking and I figured it would be good idea to go ahead and replace both mc and booster. I read a few threads about the one ton dual diaphragm booster upgrade, but everything I read was about upgrading from drum/drum to disk/drum. I'm keeping drums all the way around because I got a smokin' deal on a pair of Dana 70s with 4:10s in them. Plus I have a set of 15x10 8 lug wheels that won't fit over disk brake calipers.

I would like to upgrade my booster to a one ton booster for better braking power. The 1969 one ton booster is dual diaphragm but a smaller diameter than the 71-72 one ton booster. So here are my questions:

1) Is the 71-72 one ton booster better than the 1969 booster because of the larger diameter?

2) Will a 1969 replacement drum/drum mc work with a 71-72 one ton dual diaphragm booster since disk/drum was the only option for those years?

3)Is there a difference between drum/drum power brake boosters and disk/drum power brake boosters.... kind of repetitive if the previous question gets answered but I'm curious. The local part stores don't have any in-stock to compare.

I like the look of the later model booster better since it looks similar to the 1/2 ton booster... and I would like to use the late model braces to better support all the weight of the heavier setup. I have a 71 blazer 1/2 ton setup to donate the braces, I know the lower brace won't be long enough but I'll figure something out. I read on another thread one of the members used a spacer at the firewall. Please share your knowledge if anyone has any answers or experience with this type of upgrade.

[Lattimer]

subscribing----I'd like to know this also.

[GuyO]

I have done this exact thing, using the bigger booster from the pancake one and I saw no noticeable improvement in braking performance with front drums. There was a huge difference when I went to front disks but I understand your issue. I used the smaller diameter - bigger booster because I wanted to use my original air cleaner but upgrade to power brakes with my 250 Inline 6 cylinder. The air cleaner hit the pancake booster! The MC was the same used on both as was the proportional valve.

[seth7843]

I am also in the process of trying to figure out what the best setup for drum/drum power brakes is. So far I have found that most master cylinders for drum/drum brakes on our trucks are the non-power type (they need a long push rod). I recently bought this master cylinder (http://www.summitracing.com/parts/aaz-10-1363). It is a Cardone 10-1363. From what I can tell, it is a drum/drum master cylinder with the shallow push rod bore for power brakes. I have yet to install it to see if it works.

I'm really not sure if there is a difference between drum/drum boosters and drum/disk boosters. From what I have read, there isn't a difference. There is only a difference in master cylinders.

Good luck!

[goodemj]

Work picked up and the garage progress is suffering, I bought a new drum/drum MC for a 69' one ton and a new dual diaphragm brake booster for a 72' one ton. I had to make a longer push rod since drum/drum was no longer an option in 72' but before installing I questioned myself again.

Does anyone know why the front and rear axle ports are opposite on a one ton MC than on a 1/2 ton MC? I was initially going to make new MC-to-proportioning valve lines that would cross and correct this but then questioned why they were switched in the first place. Is there different fluid proportioning within the MC since one ton trucks were hauling heavy loads over the rear end?

I could just return the drum/drum one ton MC and get a 1/2 ton MC but then I would still wonder why they switched font/rear ports on the one ton MC.

[dutchmanz]

Originally Posted by goodemj

Work picked up and the garage progress is suffering, I bought a new drum/drum MC for a 69' one ton and a new dual diaphragm brake booster for a 72' one ton. I had to make a longer push rod since drum/drum was no longer an option in 72' but before installing I questioned myself again.

Does anyone know why the front and rear axle ports are opposite on a one ton MC than on a 1/2 ton MC? I was initially going to make new MC-to-proportioning valve lines that would cross and correct this but then questioned why they were switched in the first place. Is there different fluid proportioning within the MC since one ton trucks were hauling heavy loads over the rear end?

I could just return the drum/drum one ton MC and get a 1/2 ton MC but then I would still wonder why they switched font/rear ports on the one ton MC.

I realize this thread is over a year old at this point but did you finish the project? I may have a future project doing the same thing.

[goodemj]

Originally Posted by dutchmanz

I realize this thread is over a year old at this point but did you finish the project? I may have a future project doing the same thing.

Yes I did finish this particular project but the list is never ending.... Since the proportioning valve and lines were setup for the 1/2 ton MC I returned the one ton MC which had reversed ports since this seemed to be the easiest option to reuse my current setup and I couldn't find any info on why they they were switched or any benefits over the 1/2 ton MC. I did use the one ton brake booster for 72' model because imo it looks better than the stubby one on the 69' model trucks, but if you choose this path you will have to fabricate a longer plunger since the recess in the one ton booster is deeper than the 1/2 ton booster. The depths in both MCs was identical. I can't seem to find my pictures of the plunger or side by side comparison of the boosters but I did find one of the two MCs and a picture of the setup currently in my truck. Good luck and let me know how yours turns out or if you have any more questions.

[goodemj]

I found the pictures I was looking for last night. The three push rods pictured are: (left) 72' 1/2 ton blazer MC with disc/drum with single diaphragm booster, (middle) fabricated rod for my application 69' 1/2 ton pickup MC drum/drum with 72' one ton pickup dual diaphragm booster, (right) factory rod for 72' one ton pickup MC disc/drum with dual diaphragm booster. The 72' one ton booster requires a deeper push rod if being used with a drum/drum MC since they only came with disc/drum MCs which have a shallower depth for the pushrod to enter. I still have a brand new 72' one ton MC disc/drum in the box collecting dust because I bought them as an assembly if anyone is interested?