First hand experience with changing to the NBS master cylinder WOW!

[Tom]

Originally Posted by Red88

Bled system and found firm pedal but less braking power. No good!

Originally Posted by Red88

This is all about increasing the area of diaphram and thereby increasing the force applied thru the booster to the master cylinder and reducing the amount of pedal force needed to stop the truck.

I'm confused. You didn't have less braking power with the original booster and NBS master. You just needed more pedal effort, which is the entire point of the swap. You changed the master cylinder to get a firmer pedal, then changed the booster style to get a less firm pedal? Sounds like you just needed a correctly functioning OBS master and 10.75" booster to begin with... Your diaphram research and pictures are excellent btw!

[CDR]

Originally Posted by Tom

http://www.fullsizechevy.com/forum/g...i-install.html

So I went ahead with this mod...Really happy with the results. Timed it so I was doing brakes and hubs anyway, so the knuckles and hoses were the only added expense (under $200). I now have 14.5 inch rotors and calipers off the 2010 k1500, the other parts ( knuckle, hubs ) were from a 2002.

Finally, good brakes!!!

[Red88]

Originally Posted by Tom

I'm confused. You didn't have less braking power with the original booster and NBS master. You just needed more pedal effort, which is the entire point of the swap. You changed the master cylinder to get a firmer pedal, then changed the booster style to get a less firm pedal? Sounds like you just needed a correctly functioning OBS master and 10.75" booster to begin with... Your diaphram research and pictures are excellent btw!

Sorry if my explanation wasn't straight forward enough. In my truck the old master had a spongy pedal which also means it didn't stop very well. The NBS master had a much firmer pedal but I really had to stomp on the brakes to stop. Adding the dual diaphram booster gave me both a firm pedal and the stopping power I was looking for.

I don't know for sure if I had a correctly functioning OBS master and booster. No leaks, tested ok. I do know that the truck didn't brake very well at all. From what I read that is a common complaint of owners of these trucks. I think it's a fair assumption that the standard brakes on these trucks were not adequate for alot of owners. There were 3 different brake options on 1/2 ton trucks. Good-better-best. Good wasn't very good IMHO.

[CDR]

Red, how much thicker was the dual diaphragm booster? I was wondering how much I'd have to move the brake lines where they attach to the MC...

[Red88]

I didn't have the presence of mind to measure but if memory serves about 2". There was plenty of slack in the brake lines coming up from the frame to make the connections. I imagine factory used same lines irregardless of the booster option.

[Tom]

Originally Posted by CDR

So I went ahead with this mod...Really happy with the results. Timed it so I was doing brakes and hubs anyway, so the knuckles and hoses were the only added expense (under $200). I now have 14.5 inch rotors and calipers off the 2010 k1500, the other parts ( knuckle, hubs ) were from a 2002.

Finally, good brakes!!!

Glad it helped someone out. Did you do it to a 2 or 4wd truck?

[Tom]

Originally Posted by Red88

Sorry if my explanation wasn't straight forward enough. In my truck the old master had a spongy pedal which also means it didn't stop very well. The NBS master had a much firmer pedal but I really had to stomp on the brakes to stop. Adding the dual diaphram booster gave me both a firm pedal and the stopping power I was looking for.

I think I get what your saying now

There were 3 different brake options on 1/2 ton trucks. Good-better-best. Good wasn't very good IMHO.

So I've been researching this today as I'm bored at work. Going by rockauto's pictures, 98's came with JB5,6,7 and 8 brake systems. They all used either the 10.5" dual diaphram or they used hydroboost. I'm guessing the other styles might be earlier setups? I know a couple people who put NBS masters on vortec 1/2ton trucks and had no complaints about pedal effort so I'm assuming they all had the 10.5" from the factory....

[CDR]

Originally Posted by Tom

Glad it helped someone out. Did you do it to a 2 or 4wd truck?

4wd. Not just helped, this was like my moby dick. I've had this truck since new and really enjoyed everything else about it but was always disappointed with the brakes / options for improvement available. I was to the point that I didn't even want my family in the truck on the highway, i was afraid of a collision.

BTW, Just picked up some stuff for the rear brakes, hopefully it'll be even a little mo' betta!

[speedygonzales]

Ok I have JB5 system and lookup says they are 6400 Lb.
Here's a picture
http://i1371.photobucket.com/albums/...g?t=1403961476

Only thing I see is the "DA" sticker. So what do I have? And how do you figure it out? I didn't see anything that explains the types of diaphragms. How does the types relate to the RPO code?

I see JB8 says 10000 Lb That must be Hydraulic.

I found this on a bulletin board
JB5= front disc 11.86X1.29 rear drum 11.15X2.75 Vacuum-Double Diaphragm

JB7= front disc 12.50X1.54 rear drum 13.00X2.50 Vacuum-Double Diaphragm

JB8= front disc 12.50X1.54 rear drum 13.00X3.50 Hydraulic-Hydro-Boost

But how do you get part numbers for these boosters.

Then there is this:
http://www.oreillyauto.com/site/c/de...1305&ppt=C0066

It says it's 10.75" and used for JB5,6&7???? I don't get it.

Do I want the one that is 13" x 2.5? Do you look for the booster from a 1 ton truck?

[CDR]

Hey Speedy

I have JB6 brakes and believe I have the single diaphragm booster...With an HA sticker on it

Vacuum-boosted:
JB5 = Power Brakes, Disc/Drum, 6,400 lb
JB6 = Power Brakes, Disc/Drum, 7,200 lb
JB7 = Power Brakes, Disc/Drum, 8,400 lb
JB8 = Power Brakes, Disc/Drum, 10,000 lb

Hyrdaulic-boosted:
JD5 = Dual Power Brakes, Disc/Drum, 6,400 lb
JD6 = Hydraulic Power Brakes, Disc/Drum, 7,200 lb
JD7 = Hydraulic Power Brakes, Disc/Drum, 8,400 lb
JF9 = Hydraulic Power Brakes, 4-Wheel Discs

I believe the JB7 called for the larger DD booster you linked to. There is also a SMALLER DD booster available... Is that what you have on your JB5's?

[speedygonzales]

Originally Posted by CDR

Vacuum-boosted:
JB5 = Power Brakes, Disc/Drum, 6,400 lb
JB6 = Power Brakes, Disc/Drum, 7,200 lb
JB7 = Power Brakes, Disc/Drum, 8,400 lb
JB8 = Power Brakes, Disc/Drum, 10,000 lb

Hyrdaulic-boosted:
JD5 = Dual Power Brakes, Disc/Drum, 6,400 lb
JD6 = Hydraulic Power Brakes, Disc/Drum, 7,200 lb
JD7 = Hydraulic Power Brakes, Disc/Drum, 8,400 lb
JF9 = Hydraulic Power Brakes, 4-Wheel Discs

There is also a SMALLER DD booster available... Is that what you have on your JB5's?

I have no clue All I saw was "DA" and it measures best I can see at between 10 and 11 inches.

Now above you say JB8 was vacuum but all the information I saw was it was Hydro. If it is vacuum, I want it.

[CDR]

Originally Posted by CDR

I have JB6 brakes and believe I have the single diaphragm booster...With an HA sticker on it

Strike that… it has a DA sticker on it. It's the 10.5" dual diaphragm I believe, it's 10.5 inches wide by 5.75 inches thick from the MC to the firewall.

[CDR]

Originally Posted by speedygonzales

I have no clue All I saw was "DA" and it measures best I can see at between 10 and 11 inches.

Now above you say JB8 was vacuum but all the information I saw was it was Hydro. If it is vacuum, I want it.

And I think you're right about the JB8, a little more looking and I found:

JB8 76 88 BRAKE SYSTEM,HYD PWR DISC/DRUM

So they were hydro-boost systems installed from 1976-1988. Sorry about that other RPO lookup, I got that from another post online.

[Tom]

Yes all JB8's were hydroboost. I have the JB5 and have the dual diaphram stamped 'HA' like rockauto said I would. Not sure where the single diaphram is used....

[speedygonzales]

So is the JB7 really 13" and if so, how do I find it?

Or should I just try making a slightly longer intermediate rod?

[LEEVON]

Did the MC upgrade, and bled the whole system. Pedal feels great, although overall braking effectiveness is pretty much the same. I would like to add the dual-diaphram booster, 3/4 ton calipers and Powerstop drilled and slotted rotors.

[CDR]

Upgrading from a single diaphragm booster to a DD should make a noticeable difference. The 3/4 ton calipers should take advantage of your new MC as well. Just remember the 3/4 ton pads will rub your rotor hat, so either use 1/2 ton pads or grind down the metal backing plate on the 3/4 on pads.

I liked my powerslot rotors (not drilled though), hope they treat you well!

[CDR]

Originally Posted by speedygonzales

So is the JB7 really 13" and if so, how do I find it?

Or should I just try making a slightly longer intermediate rod?

Hey Speedy-

Did you make any new findings on the JB7 booster?

[Tom]

Originally Posted by CDR

Just remember the 3/4 ton pads will rub your rotor hat, so either use 1/2 ton pads or grind down the metal backing plate on the 3/4 on pads.

I've had a couple sets of 3/4ton pads on my 98 that also has the larger piston 3/4ton calipers and 1/2ton rotors, never had a rubbing issue.

[speedygonzales]

Originally Posted by CDR

Hey Speedy-

Did you make any new findings on the JB7 booster?

Nope never found anything

[El conquistador]

Just did this on my truck and the results were great. After I did it though, I was doing some reading online and the "store bought" version of this upgrade from SSBC shows the adapter going in the rear port and reversing the brake lines.
http://www.summitracing.com/parts/ssb-a0463

instructions...
http://ssbrakes.com/attachment/63706...ction%20Manual

Any ideas?

[CDR]

You may be referring to the design change on the NBS brake circuits being flipped F/R?

With our trucks using the step bore master the front circuit had to use the forward portion of the cylinder to drill the stepped bore ( can't put a bigger bore bit thru a smaller bore hole)

Since the nbs uses the same bore size for both circuits, the engineers chose to reverse the layout, but they should operate identically.

[CDR]

Hey Speedy,

Since we dusted off this thread I thought I'd mention that the nnbs trucks added an electric vacuum pump to the brake systems. I plumbed one up to see if i could feel any difference...

[Keith Seymore]

Originally Posted by speedygonzales

Nope never found anything

I apologize for not thinking of this sooner: I have the brake system release charts from the brake engineer for the '74 and '87 trucks C/K/R/V squarebody versions.

While not totally germaine (I do not have the corresponding GMT400 versions) it will give you an idea of the proliferation and the way the components are structured and named (by part number and broadcast code).

I don't see the "DA" coded booster on here but you can imagine where it would go. One of the ways you would find the corresponding part number for the "DA" booster would be finding a chart like this and working backwards.

For your entertainment:

[CDR]

Thanks, that's pretty sweet. Wish we had them for the 400/800's !