The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - First hand experience with changing to the NBS master cylinder WOW!

CDR · 06-28-2014, 10:10 AM

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?

06-28-2014, 10:10 AM	#85
CDR Registered User Join Date: Apr 2014 Location: Colorado Posts: 25	Re: First hand experience with changing to the NBS master cylinder WOW! 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?