1/2 ton to 1 ton brake upgrade

[cstanley]

ok, this is my thread chronicling my swap from a '72 1/2 ton vacuum booster/ master cylinder for a 1 ton dual diaphragm setup, for more braking power. inspiration came from this thread http://67-72chevytrucks.com/vboard/s...d.php?t=206615

so, this is where i started, my original existing setup.

[cstanley]

and the comparison between the booster sizes. relatively the same.

[cstanley]

now for the uncertain part...will it fit?

the answer: mostly.

[cstanley]

the parts that, so far do not fit, are the lower bracket that goes from the front of the booster to the firewall, a few inches from the steering column penetration (yeah, i said it.)

the other problem, and the cause for pause in the work for the night, is that the old steel brake lines between the new 1 ton m/c and the 1/2 ton proportioning valves have slightly different sized fittings. i'll have to run to town tomorrow and try to find a few lengths of the proper sized brake lines.

the problem is that the fittings to the m/c need to be swapped, as the front one now fits the rear, and vice-versa.

anyway, here's how she sits tonight. overall i'm happy with the fit, as long as i can make my proper brake lines tomorrow, or else i'll have to find a 1 ton proportioning valve... i didn't have to make any other mods yet, but i don't know how i'm going to solve the front lower bracket, if i even need it.

[msgross]

does the hood shut? where did you get your item? I am starting with drum/drum manual with no PB. looking to buy a bracket and get new items like you did. the stock wheel cylinders should hold up, right? thanks

[ERASER5]

CStanley, your new mc looks similatr to the one ont the booster/mc kit that I was looking at. That gives me some hope anyway.

[cstanley]

hey everyone, an update.
much to my chagrin, i have abandoned this conversion for the time being. i am confident everything will work, the hood shuts, no clearance problems - but
my conversion was getting to be more expensive than i wanted, as this will require the 1 ton proportioning valve set up, which i do not have, nor do i have access to one. it also requires the 1 ton lower bracket.

so, just to be clear, as far as fitment goes, this conversion will work. i just don't have a spare 1 ton truck around that i could get the remaining prop. valve and bracket off of. i needed to get the truck back on the road, so i just grabbed the readily available 1/2 ton m/c and booster from the local autoparts store, and will be returning the 1ton parts.

did i mention i was disappointed?
oh well, perhaps in time i will run across the necessary parts in a wrecking yard, then i will definitely do the conversion.

[HuggerCST]

Thanks for all of the info and pics. I wouldn't think that you would need the lower support bracket. Especially since the dual diaphram booster will take less foot effort. My '70 didn't even come with the support brackets. Also, won't the prop valve from a 3/4 ton work also?

[70rs/ss]

Guys, I used my 1/2 ton proportioning valve, simply by rebending the lines till they went to the right spot. For some reason the front to rear location relative to the master cylinder is different (on the half ton the front resevoir is the rear brakes and on the 3/4 ton the front resevoir is actually the front!) so just reroute your 1/2 ton lines till they fit the 3/4-1ton master cylinder. AGAIN, YOU DO NOT NEED A 3/4-1 TON PROPORTIONING VALVE!!

[HuggerCST]

Originally Posted by 70rs/ss

Guys, I used my 1/2 ton proportioning valve, simply by rebending the lines till they went to the right spot. For some reason the front to rear location relative to the master cylinder is different (on the half ton the front resevoir is the rear brakes and on the 3/4 ton the front resevoir is actually the front!) so just reroute your 1/2 ton lines till they fit the 3/4-1ton master cylinder. AGAIN, YOU DO NOT NEED A 3/4-1 TON PROPORTIONING VALVE!!

Hey 70, would you mind posting pics of yours, and let us know what parts you did have to use from the 3/4, or one ton? I just want to be clear about it. It seems this has been a pretty grey area lately.

[cstanley]

aw crap. that would have been good to know. so i can just swap the lines?

[JameslovesJammie]

Anybody attempting this?

[70rs/ss]

Ask and you shall recieve, and for those of you with a keen eye, you can see with some persuasion and the addition of a thin spacer, the brace will work as well. This is a very straight forward deal, unbolt 1/2 ton booster, buy 72 3/4 ton booster (and master cylinder as it is a few bucks more when purchased together) and bolt it in the place of the 1/2 ton. Rebend the lines and pursuade the brace, tada, it fits and will throw you through the windsheild with the slightest effort!!

[msgross]

Wanted to buy ads are not allowed unles you are a subscribing member.

[cstanley]

sweet. i boogered up my original lines, and got some new ones last night. i will be resuming my efforts this evening, and will hopefully have a working system tonight! Game On!

[cstanley]

ok, i finished the swap. the only major thing i have to say about it is...



OMG!!!

my face is still hurting from being slammed into the windshield!!!!

i know this thing has never stopped this well in the 12-13 years i've owned it, and the 4 years prior to that my brother owned it...

i still don't think i have completely bled the lines (but maybe i'm too used to the rock-hard pedal that didn't move much.)

i did have to make new lines (picked up a couple of 8" pre-flared lines from pep boys.) i did have to use an adapter, but it works great!

pics below

[HuggerCST]

Originally Posted by cstanley

ok, i finished the swap. the only major thing i have to say about it is...



OMG!!!

my face is still hurting from being slammed into the windshield!!!!

i know this thing has never stopped this well in the 12-13 years i've owned it, and the 4 years prior to that my brother owned it...

i still don't think i have completely bled the lines (but maybe i'm too used to the rock-hard pedal that didn't move much.)

i did have to make new lines (picked up a couple of 8" pre-flared lines from pep boys.) i did have to use an adapter, but it works great!

pics below

I'm glad to see that it all worked out for you!

[ERASER5]

Originally Posted by cstanley

OMG!!!

my face is still hurting from being slammed into the windshield!!!!

I only hope to one day feel your pain...

[70rs/ss]

Originally Posted by msgross

Wanted to buy ads are not allowed unles you are a subscribing member.

WTF?! I really didn't see anyone trying to buy or sell, anyone.....

[msgross]

oops, I guess I mentioned that I needed a set of brackets... they took that as a WTB post...

I plan on paying to support the site, just low on funds this month.. sorry admin dudes!

[70rs/ss]

The brackets from the 1/2 ton booster will work, unless you are switching from manual to power, then you'll need the brackets. You can find them at a salvage yard for next to nothing and anything from the early 70's up should fit, as for the $25, you don't need to pay it unless you want to buy and sell, its free to hang out.

[aboyer]

I am running into the issue where I have upgraded to the 3/4 booster, but I think the brake pedal rod is not long enough.

--I have bleed all the brake lines complely and M/C
--Purchased a new MC/Booster
--New Disc/Disc port valve

But I still have a very very weak brake pedal. I can't figure it out. I have also changed to the bigger booster brackets that are 4in long.

Does anyone have any suggestions??

Adam

[LUV2XCLR8]

So how does she stop ? ? ?

[aboyer]

To stop her, I have to push the brake pedal down is far as it goes. When I get to the end, it finally stops. It is not a strong stop, just a very weak stop.

Do you think I need to adjust the brake rod on it? Do you suggest a certain length?

Adam

[cstanley]

Originally Posted by aboyer

I am running into the issue where I have upgraded to the 3/4 booster, but I think the brake pedal rod is not long enough.

--I have bleed all the brake lines complely and M/C
--Purchased a new MC/Booster
--New Disc/Disc port valve

But I still have a very very weak brake pedal. I can't figure it out. I have also changed to the bigger booster brackets that are 4in long.

Does anyone have any suggestions??

Adam

any pics?
(i don't really know anything about these conversions, except for the one i did on my '72, and even there i just know enough to be dangerous.)

btw, mine still stops like mad! before the conversion it would lock up the rears at the slightest stop. now it doesn't have that problem. i will have to say that it's taken some getting used to. the brakes are...touchy.