How to: NBS master cylinder swap for firm brake pedal

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Frankp

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I did this over the weekend and the adapter listed in the OP did not fit my old lines. I had to get the BLF 18C from Auto zone and not the BLF 26, it was slightly too big for the brake line fitting.
 

Knuckle Dragger

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Did anyone of you guys install a inline residual valve? The disc/drum master should have had an internal valve where this disc/disc master won't. In theory it should bring the pedal a little higher as well as keep some pressure on the rear cylinder seals so they don't suck air. I did the swap using a master and hydroboost from an 05 3500. The pedal is OK but I haven't pulled it off the stands yet to drive it.
 

Knuckle Dragger

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Nobody ran a residual valve? I'll post again because I think it's important and part of making the modification the right way. Not having the residual valve will "relax" the rear cylinder cups and allow air to enter the system. It's the only way air can enter the system with out a leak. The valve was $10 off eBay, Wilwood has them for about $20. They come in 10# and 2#, you want the 10 for drums. I replaced the line because I didn't want the adapter at the master and since I was flaring lines I might as well do it right. This is a in process picture so it's a little messy but it gives you an idea.
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east302

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Knuckle,

I was wondering about this, too. Did any of the 99-06 come with disc/drum setup? I vaguely remember that they went back to rear drums in the later year models.

Did you end up having to bleed the ABS unit?

EDIT: Looks like they went back to drums on the 2005 1/2-ton pickups with the lower GVWR. AC Delco and rockauto show two designs for the vacuum booster disc/drum on the 2005 Silverado 1500, the difference being in how the reservoir attaches (which I don't think would matter to us) and the connection point at the booster--which would matter, the first design extends further into the booster than the second design. First design part is Delco #174-1011 the second is Delco #174-1169. I think the second looks like the GMT400.
 
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Brandon_Lutz

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After reading this thread, I am thinking about doing this on my 95 K2500, if I read correctly all NBS 2500's are hydro-boost correct? If so and I want to just keep my vacuum boost, should I look into a 1500 MC?
 

Justin S

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OK after looking through this whole post, either I missed it or it just wasn't stated. I have an OBS hydroboost pump that i'll be putting in my 93, and I want to use a NBS MC. Can I just buy a NBS one that is meant for hydroboost and bolt it right up, or is there something different as to where I should use a NBS 1500 MC and trim the booster to fit?
 

DRAGGIN95

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For gmt 400 with Hydroboost you either run a stock 88-98 Hydro. M.C., or you can bore out the inside of the hydro unit to accept the NBS Hydroboost M.C. I have done both, I have the NBS Hydro. M.C. on my personal truck, I used a M.C. from an 04 tahoe with hydroboost, then I bored out my hydroboost unit with an air rotary file and lots of wd 40 to keep it cool as I was doing it, as I did mine on the truck, you could also use cutting fluid or something similar.
 

Justin S

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Thanks for the info! I wasn't sure if it was only necessary to modify it if a NBS vacuum MC was used.
 
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