Jb5 to jb7 master

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Imup5-0

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Can anyone tell me if the jb7 master cylinder will work on the jb5 booster or do I need the jb5 master and booster? I cannot find a definite answer
 

Ed_P

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he's upgrading his brakes... Interesting post . Perhaps I can find out my brakes by the master. Im thinking JB7 but the code is nowhere to be found. I have another thread on this subject
 

Ed_P

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JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder

JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"

JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder
 

Imup5-0

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I am trying to upgrade my master cylinder. Everywhere I've read tells me the jb7 mc will work on jb6 booster but I cannot find out if the jb7 mc will work on the jb5 booster. I'm really trying to get rid of the pedal travel.
 

Imup5-0

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JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder

JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"

JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder

From the looks of this the jb5 and jb7 mc are the same so it should work right?
 

evilunclegrimace

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It will bolt up but if you have the low drag calipers you will most likely not notice any big difference in pedal travel
 

Imup5-0

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It will bolt up but if you have the low drag calipers you will most likely not notice any big difference in pedal travel


I plan to upgrade to the jb7 mc and calipers. That's exactly why I needed to know if the jb7 mc would work with the jb5 booster. From my understanding the jb7 calipers are all conventional(not low drag). Am I correct to think this?
 

shamrock246

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I plan to upgrade to the jb7 mc and calipers. That's exactly why I needed to know if the jb7 mc would work with the jb5 booster. From my understanding the jb7 calipers are all conventional(not low drag). Am I correct to think this?

From what i understand the calipers with the 75mm pistons(1/2 ton) are the low drag type and the 80 mm and 85 mm (3/4 and 1 ton) are conventional type. Not sure about the booster will they let you test fit it at he store or will a JB6 booster fit in your truck?
 
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