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

[dragginmetal]

What's the difference in a JB system and a JN? My 88 has a JN.

[Keith Seymore]

Originally Posted by dragginmetal

What's the difference in a JB system and a JN? My 88 has a JN.

Attachment 1338074

Just the RPO designation.

I suspect it was changed to avoid confusion with the the carryover C/K/R/V vehicle (ie, carryover got "JBx", new GMT400 got "JNx" for a comparable system).

K

[speedygonzales]

It also appears that the original MC in the vehicle has twice the volume output from the rear port vs the front port According to the page posted by Keith. Which is usual for GM where the larger back reservoir feeds the front brakes when there are front disk and rear drums.

So what about the new style MC? Does it have a difference from the front and rear ports? If it does, I should switch the ports like the SSBC says to do. If it doesn't make a difference than switching won't do anything bad. It sounds as though I may try switching the ports. I'm about ready for a bleed anyway.

I'll let you know what happens.

[speedygonzales]

I know the most powerful is the hydro JB8.

The question I already asked was isn't the JB7 the most powerful vacuum booster? And are the pages you printed showing the "DA" is a JB7

The whole reason this discussion of boosters came up because someone changed from a single to a double. So my natural question is do I have a single or a double? It has "DA" on it and I already posted it's dimensions. Once I figure out what mine is, I can determine if a more powerful booster is available. Capish?

[speedygonzales]

OK my RPO label says "JB5
I have 11" rear brake pads (I know cause I just changed them).
The booster label is "DA"

There is this from earlier
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

The page posted by Keith lists under the JB7 column the booster as
18024268/DA
Is that the sticker on it?

If a JB5 is supposed to be the lesser of the three as far as power, why would a JB5 system have a JB7 booster?

Who can help with the booster I have?

[Keith Seymore]

Originally Posted by speedygonzales

I know the most powerful is the hydro JB8.

The question I already asked was isn't the JB7 the most powerful vacuum booster? And are the pages you printed showing the "DA" is a JB7

Yes, and yes.

Originally Posted by speedygonzales

The whole reason this discussion of boosters came up because someone changed from a single to a double. So my natural question is do I have a single or a double?

240S = single
240T = "tandem" = dual
So you have a "double" already.

Originally Posted by speedygonzales

It has "DA" on it and I already posted it's dimensions. Once I figure out what mine is, I can determine if a more powerful booster is available. Capish?

Absolutely.

Originally Posted by speedygonzales

OK my RPO label says "JB5
I have 11" rear brake pads (I know cause I just changed them).
The booster label is "DA"

There is this from earlier
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

The page posted by Keith lists under the JB7 column the booster as
18024268/DA
Is that the sticker on it?

Yes

Originally Posted by speedygonzales

If a JB5 is supposed to be the lesser of the three as far as power, why would a JB5 system have a JB7 booster?

Because aaaaaaaaaaaaaaaallllllllllllllll those other components listed on that chart make up the brake system; not just the booster.

Originally Posted by speedygonzales

Who can help with the booster I have?

I'm not sure...

K

[speedygonzales]

Originally Posted by speedygonzales

I know the most powerful is the hydro JB8.

The question I already asked was isn't the JB7 the most powerful vacuum booster? And are the pages you printed showing the "DA" is a JB7

Originally Posted by Keith Seymore

Yes, and yes.

So???????????? Doesn't this answer the question????????? The JB7 is the most powerful and you said yes the DA is a JB7.

Am I missing something?

[Keith Seymore]

Originally Posted by speedygonzales

So???????????? Doesn't this answer the question?????????

Yes

Originally Posted by speedygonzales

The JB7 is the most powerful and you said yes the DA is a JB7.

Yes

Originally Posted by speedygonzales

Am I missing something?

I'm beginning to wonder.

K

[speedygonzales]

Originally Posted by speedygonzales

Who can help with the booster I have?

Originally Posted by Keith Seymore

I'm not sure...

Originally Posted by Keith Seymore

I'm beginning to wonder.

Your original response was you weren't sure. Do you not understand my confusion?

DA=JB7 the most powerful vacuum booster there is on a 1998 So there is no need to look for a more powerful one. Any more gains will come from either boosting vacuum or something else.

[JTWard]

I know I'm getting in on this subject a little late, But I got a hell of a problem with the brakes on my 1990 1/2 ton 2WD. I came home from visiting a Marine Buddy in a re-hab and on the way home I had to stop short and really put my right foot into it and I still wound up a part way into the cross road ?. I have replaced everything, new Husky Lite truck pads, new rotors, stainless steel brake lines , bleed the thing 3 times and still you can't get this thing to lock up the brakes, I know I have the ABS module for the back drum brakes. . . but that isn't even worth the effort to toss away as their useless. The brake pad is like stepping into soft new dug up dirt. your foot just keeps going down. It's a 1990 1500 Silverado with a 5600 weight capacity. It's got a 5.0 liter 305 V8 !


So fellows, I'm lost on this thing. I've got a 5600 pound weight rating but I'd be afraid to put a 1/4 ton or try to tow 10,700 tow capacity. I'd never be able to stop, I can't stop with an empty bed ! Please throw me some life saving info to help. I just got down a 3 year full body off restoration. I need help !

[El conquistador]

Brake fluid looks mighty dark in the photo. But it could be the pic. Did you change the master cylinder? If not, ditch it for the NBS master. Also, doid you replace the flexible lines?

[CDR]

JT, you have a step bore MC. The swap to the NBS MC will firm up the feel of the brakes. The knuckle swap and 14.5 inch rotors I did on my 4x4 were the problem solver for me, but won't work on your 2wd rig.

The mc swap is cake, I'd recommend it.

[speedygonzales]

Change out the MC
Bleed as required
Start a new thread

[Kudzupatch]

FYI Tried this on a 1993 Suburban with the large 4 wheel anti-lock module and it would require pretty serious line bending. I think it would ended up crimping the line. I think it would be simpler to just make new lines between the proportioning valve and the MC.

My MC gave up and I had to replace it so I can go a trip. So I went back with a replacement unit. Will look at this latter when I have time.

[JTWard]

Originally Posted by Kudzupatch

FYI Tried this on a 1993 Suburban with the large 4 wheel anti-lock module and it would require pretty serious line bending. I think it would ended up crimping the line. I think it would be simpler to just make new lines between the proportioning valve and the MC.

My MC gave up and I had to replace it so I can go a trip. So I went back with a replacement unit. Will look at this latter when I have time.

Thank you, Prior experience is exactly what I need !

[green_grenade]

I am doing the NBS MC swap this weekend. It looks fairly easy. I am hoping it looks as easy as everyone says it is. Can't wait to see if this actually helps on this truck.

How do I find out for sure if I have the light duty 3/4 ton? Mine is a 89 and has the 2500 side moldings, but when I run the codes in the glove box I don't have a F44. Mine is a 6 lug also.

[BigRed76]

Originally Posted by green_grenade

I am doing the NBS MC swap this weekend. It looks fairly easy. I am hoping it looks as easy as everyone says it is. Can't wait to see if this actually helps on this truck.

How do I find out for sure if I have the light duty 3/4 ton? Mine is a 89 and has the 2500 side moldings, but when I run the codes in the glove box I don't have a F44. Mine is a 6 lug also.

Light duty 3/4 ton will have a 7200 GVW.

[green_grenade]

Originally Posted by BigRed76

Light duty 3/4 ton will have a 7200 GVW.

Thank you very much. That is exactly what mine says 7200 GVW.

[Tom]

Look at the GVW on the door plate.

[cmcolfax]

Bumping this thread for reference as my 96 K1500 Burb is going under the knife for significant brake, steering and suspension upgrades in a coupla weeks.

Looks like I am gonna pick up a NBS MC...

[VentureRick]

WOW, I just did the swap on my 95 K1500 Suburban and this thing has never had brake's this good, I can't believe the difference.

[54 jimmy]

night and day difference. now towing trailer will be a lot more safe.

[OutlawDrifter]

speedy, did you ever swap lines to see if it made any difference?

[speedygonzales]

No I completely forgot. Man I don't know if I want to have to bleed the thing all over again. I'll post up if I do it.

[OutlawDrifter]

no worries, i've got to put some new wheel cylinders on my pickup, so i'm going to do the mc at the same time. just thought i would see if you ever tried it!