To all those planning on a nbs master cylinder swap

[beardeddummy]

The nbs master cylinder is meant for rear disc. That being said if have rear drums they require a constant 10psi the obs master cylinder has a provision for this. The nbs mc does not. Yes it will work but you will no longer have rear brakes. On most of these trucks the back brakes dont work unless you adjust them. Anyways my boss a mechanic with over 20 years experience educated me on this and i figured it ought to be shared. Im not trying to say i know it all but i have learned when it comes to the mechanical side of things if he tells me that the sky is green i need to find a storm shelter

 

[90halfton]

Swapped mine and my rear brakes work amazing. Much better than before. And I keep them adjusted properly

 

[east302]

That's a good point, bearded.

I would look for a master cylinder for the Silverados that had the disc/drum setup. I think it was in 2005 when they went back to that on the lower GVWR models. Those should have the residual valve integral to the master cylinder like the GMT400.

The 99-04 would not and, in theory, would require the valve to be installed on the rear brake line outlet at the master cylinder. I believe that it keeps pressure on the cylinders to keep them from drawing in air when they retract.

 

[90halfton]

Believe mine was intended for an 02 model. Should it not be working? Tested brakes after install and the rears locked up amazingly on a dirt road. I'm not second guessing your logic or knowledge. Just wondering if I'm running the wrong thing. Got this idea from many threads of ppl doing this

 

[beardeddummy]

I was a little wrong they will work just not as good as they i am gonna use a 1 ton mc its a much larger bore so should give much better pedal will update as it develops

 

[east302]

Yeah, that's what I don't get when I read of people that successfully made the swap. But, hey, if it works then...well, go with it. I'm thinking of doing it on my 98 but will probably look for a disc/drum MC just in case.

Is the pedal feel significantly improved over the GMT400 master?


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[beardeddummy]

Im not sure but your gaining 1/4inch of bore size i beleive so it should help the pedal feel alot

 

[98sierra4x4]

I swapped an nbs master in my truck. No problems at all. I can lock up the rears in the rain really well. The rears work just as well as before. I think my MC was from a 99-04 truck too although im not sure. Much better than the obs master imo.


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[beardeddummy]

Does your 14bolt have 3/4 ton brakes if so they will grab harder in turn locking up easier

 

[98sierra4x4]

Does your 14bolt have 3/4 ton brakes if so they will grab harder in turn locking up easier

I forgot all about that! Yes it does. That may explain it.


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