Seeing mixed answers on using a NBS master cylinder with an obs that has a vacuum booster

[88sclb350]

Can I buy and install NBS master cylinder with the fitting that's also required right onto an 88 1500 with a vacuum brake booster, some places i see people say you cannot, some people say you should not. Looking to get a better brake pedal and was hoping to do this swap but now not sure if i can or not

 

[Erik the Awful]

You're not going to truly and safely "fix" the brakes by swapping to a GMT800 master cylinder that's not really compatible with our brakes, but that doesn't stop people from doing it.

If your '88 came with JB5 brakes (if it came with a 350, it likely has JB5), your best bet is to adjust the rear brakes as close as you can, flush the brake fluid and bleed it, and install Raybestos Element 3 pads. My '89 has nice JB5 brakes. They'll never be comparable to my Mustang's brakes, but they're good.

If you want to upgrade to brakes that feel like a modern sports car, call Wilwood and prepare to set your wallet on fire.

 

[L31MaxExpress]

You're not going to truly and safely "fix" the brakes by swapping to a GMT800 master cylinder that's not really compatible with our brakes, but that doesn't stop people from doing it.

If your '88 came with JB5 brakes (if it came with a 350, it likely has JB5), your best bet is to adjust the rear brakes as close as you can, flush the brake fluid and bleed it, and install Raybestos Element 3 pads. My '89 has nice JB5 brakes. They'll never be comparable to my Mustang's brakes, but they're good.

If you want to upgrade to brakes that feel like a modern sports car, call Wilwood and prepare to set your wallet on fire.

Could always upgrade JB5 to what my Tahoe came with. It had a larger bore master cylinder, larger dual diaghram booster, larger 11" drums and the larger 8800gvw style front calipers. GM put the same brakes on the Police Tahoe and Tahoe Limiteds but my 99 was ordered with them as well as a factory tow package. The only change I made to that setup was a hydroboost conversion and it stops on a dime.

That being said a NBS master cylinder is not a working upgrade without ditching the low drag calipers and upgrading the booster. I put one on my 97 van years ago when it was all the rage to do. Ended up finding myself with both feet on the brake pedal, literally standing my whole 300 lbs body on the pedal to get it to shut down when someone pulled out in front of a couple of cars in front of me. Now that I am 60 lbs lighter, I would have rear ended all of them for sure.

Hydroboost would be a great upgrade.

I recently put a NBS Express van (2005 G3500 application) master on my 97, but I also swapped to the matching hydroboost that has a larger piston for more boost pressure and no longer have low drag front calipers that require a quick take-up master cylinder. I have 1-ton dual rear wheel front calipers and the matching thicker 01-02 3500 van rotors. I am still not a fan of the way that master cylinder feels, but it does have enough braking power to kick the ABS in at ~50 mph.

 

[OutlawDrifter]

Having done the NBS master on a '95 Sierra, don't waste your time with that. I bought in to the hype and was disappointed.

If you want good brakes, Hydroboost is the best bet for stock fitting parts. Otherwise learn to live with the fact that GMT400 vacuum brakes are just, okay.

 

[L31MaxExpress]

Having done the NBS master on a '95 Sierra, don't waste your time with that. I bought in to the hype and was disappointed.

If you want good brakes, Hydroboost is the best bet for stock fitting parts. Otherwise learn to live with the fact that GMT400 vacuum brakes are just, okay.

Agreed, never understood why the full size trucks, SUVs and Vans had vacuum boost from the factory yet the lighter Astro vans got hydroboost. After driving an 80s diesel Cadillac Fleetwood, a late 90s Astro and a 1994ish G20 van with hydroboost all in about the same week, I bought the stuff and converted my 83 G20 to hydroboost. Then followed with my 97 Express a couple of years later.

 

[HotWheelsBurban]

JB 6 brakes are what the 1500 Burbs came with, and would be a great upgrade for the 1500 pickup. Some Tahoes have this option, but all the Burbs did. The "barely adequate" brakes on 400 half ton pickups was one major factor in my search for and eventual acquisition of an 8 lug truck....
No disrespect meant to all the 1500s out there, but your trucks ' stock brakes need help.

 

[L31MaxExpress]

JB 6 brakes are what the 1500 Burbs came with, and would be a great upgrade for the 1500 pickup. Some Tahoes have this option, but all the Burbs did. The "barely adequate" brakes on 400 half ton pickups was one major factor in my search for and eventual acquisition of an 8 lug truck....
No disrespect meant to all the 1500s out there, but your trucks ' stock brakes need help.

It has been a while since I looked at the labels, but IIRC the Express was JB6 and the 99 Tahoe was JB7.

JB7 is usually for ~7,400 GVW but some of the 5 lug Tahoes used the calipers and master cylinder from the 7,400 gvw trucks along with the JB6 11" rear drums.

 

[Schurkey]

You're not going to truly and safely "fix" the brakes by swapping to a GMT800 master cylinder that's not really compatible with our brakes, but that doesn't stop people from doing it.

SO true.

If your '88 came with JB5 brakes (if it came with a 350, it likely has JB5),

My '88 has a 5.7L LO5, but still had the crappy JN3 brakes.

So far as I know, '88--early '1990s (perhaps '91 or '92) regular-cab 1500 pickup trucks had JN/JB3 brakes, extended-cab 1500 trucks had JN/JB5 unless ordered with an upgraded brake system, perhaps as part of a "towing package".

At some point in the early 1990s, GM realized that the "3" brakes (JN3, JB3) were garbage, and they quit offering them. The "5" brakes (JN5, JB5) became the basic "power" brakes even on regular-cab 1500 pickups.

I've never seen a GMT400 with manual brakes, but it's option code JN1, and--I guess--is just the manual version of JN3.

your best bet is to adjust the rear brakes as close as you can, flush the brake fluid and bleed it, and install Raybestos Element 3 pads. My '89 has nice JB5 brakes. They'll never be comparable to my Mustang's brakes, but they're good.

If you want to upgrade to brakes that feel like a modern sports car, call Wilwood and prepare to set your wallet on fire.

The most cost-effective upgrade is to use the booster, master, front calipers, front rotors, and front hubs from an extended cab truck or other JN5/JB5 donor, replace the seized park-brake cables, and USE the park brake OFTEN, so that the horse-crap 254mm (10") Leading-Trailing shoe rear brakes stay in adjustment. If you buy the complete front brake system from the Treasure Yard, it's a downright bargain even if you have to replace some of the "used" parts--at least you can turn them in as cores.

You must be registered for see images attach

Better still is to use all that JN5/JB5 stuff, and upgrade to the 11.x Duo-Servo rear brakes. Easy on a K1500, harder on a C1500. Just get a "light-duty 2500" 6-lug axle of the correct gear ratio, swap the entire axle brake-drum-to-brake drum.

This gets you "JN6/JB6" brakes. Works great on a 1500.

Otherwise learn to live with the fact that GMT400 vacuum brakes are just, okay.

The biggest problems with GMT400 vacuum brakes are:
1. The entire JN3/JB3 brake system. Wimpy booster, small master cylinder bore, small caliper piston bores, thin rotors and the horrible 254mm leading-trailing rear drums.
2. The horrible 254mm leading-trailing shoe rear drums also infecting the JN5/JB5 brake system. But at least the "5" brakes are adequate up front.
3. The under-engineered RWAL system, in particular the later aluminum-bodied ones that don't have the bleeder screw that the iron ones did, and therefore need a scan tool to bleed properly.
4. All the other ABS systems that need a scan tool to bleed properly, which usually means they've never been bled properly since the truck was new, decades ago.

The JB6 brakes--properly bled, with decent friction material, return springs, properly adjusted, etc (in other words, working like it's SUPPOSED to) is perfectly adequate on a 1500. It's what these trucks should have been equipped from the beginning.

JB 6 brakes are what the 1500 Burbs came with, and would be a great upgrade for the 1500 pickup... ...No disrespect meant to all the 1500s out there, but your trucks ' stock brakes need help.

Yup. The 1500 pickups had marginal ("5") or terrible ("3") brakes unless specifically ordered with improved "optional" brakes. But the JN6/JB6 are fine.