3/4 - One ton Master Cylinder upgrade

[jjzepplin]

So I have an older Steel master cylinder that has that older seepage type leak and I am going to just replace it. I am looking to see if anyone has upgraded the unit to a stock type newer style with the plastic reservoir from a newer truck. So the truck has one ton axles with front disc rear drum. Dana 60 front 14 bolt rear. The current master was robbed from a junk yard square body 3/4 ton.
I guess I could just get with Wilwood or Bear and see what they have but I have no experience with either. I kinda prefer something I can get locally.

I am looking at this.

https://www.rockauto.com/en/moreinfo...t=1836&jsn=554

[907burb]

I'm not sure what a newer style would do for you to improve performance. I do not have a later style master cylinder. For what its worth, I have a dana 60 front with 14 bolt on my 68 burb. The 14 bolt has the one ton wheels cylinders with 13 inch brakes. I bought a new 72 3/4 ton cylinder and booster from NAPA and put all new brake lines on it, the brakes work very well. I considered buying a hydro brake setup, but didn't want the headache of an oddball system that could be hard to get parts for in the future. NAPA had the all the brake parts for the front and rear to include master cylinder/booster.

[57taskforce]

I would suggest a 1ton square body master. What type of booster are you running? There was a noticeable change in brake feel with my hydroboosted 3/4 ton master when I went from the Dana 44 to the front 60. It still stops good but the feel is different. The square body master has a different bore to match the higher displacement of the 60 calipers. I’m really not sure what later style master’s would fit that bill.

[jjzepplin]

I am really just looking to get away from the leaky old style masters. My booster is a stock style robbed with the master. I got the whole assembly from the firewall forward.

[Orange Crate]

Be aware that 85 K30 and 84 K5 (with deisel) have the reservoirs swapped. The K5 is normal front rez to front system, the 85 K30 is reversed. I'm looking at the K5 for larger diameter cylinder bore (1.18 "). Stock was/is 1.125. K30 bore is big at 1.3"

[57taskforce]

I know that in my case I’m using a hydroboost from an 09 Silverado with a factory style aftermarket 72 K20 master cylinder. That would lead me to believe that the late model trucks use the same pushrod length as the old trucks. If you got a master for say an 01-07 HD truck that had drum rear brakes (they could be had that way) you’d probably be pretty close to what you’re wanting to do. Might be worth looking into. I’m not sure if the GMT 900 (07-14) HD trucks could be had with rear drums but if they could that might open it up even more.

[jjzepplin]

That is great information! Thank You! Do these newer systems still use a proportioning valve? I was thinking that as long as the newer master bolted up and the pushrod was similar that the proportioning valve would handle the distribution of the fluid correctly.

[57taskforce]

Unfortunately they don’t because the function of the proportioning valve is built into the abs. However a few years ago I deleted abs from a GMT 400 (88-98) truck and used a square body proportioning valve with no issues at all. I’d bet also you could make the OE proportioning valve work too, The trick to doing this on a 67-72 is that the later stuff is metric thread on standard American size line. Once you get your proportioning valve mounted up you’d have to have metric inverted flare nuts for the master and SAE nuts on the side for the valve. The line size should be the same. If you use a later square body valve all you should have to do is cut the SAE fittings off the existing front and rear lines coming out of the proportioning valve that go to the wheels and replace them with metric nuts. This would probably be the easiest way to do it but a 71-72 valve should work fine too, just a bit more complicated.

[jjzepplin]

So couldn’t I just put metric ends on the newer master cylinder side of the old lines?

[Richard]

Installed a master from a 2006 2500HD in my 72. The tube nuts were not metric. 1/2"x20 IIRC. Will check if you want. Hydroboost as well. The modified Hydroboost I ordered and installed was for originally specked for the 72 master. Used an aftermarket adjustable proportioning valve. Everything seems okay at this point. I have not bled the system yet. Rod length seemed okay. Will see results soon.

[jjzepplin]

I am very interested in your setup Richard! What axles are you running?

[Richard]

Originally Posted by jjzepplin

I am very interested in your setup Richard! What axles are you running?

The rear is an AAM 11.5 from a 2006 2500HD. 13" rotors with drum type parking brake.
Front is a custom high pinion D60 built by East Coast Gear. I installed 2009+ Ram 3500 calipers and 14" rotors.
There is info and pics in my thread about other components. I used 3/16" brake line when making new lines.
Installing an EStoppe unit to actuate the park brake.