Is this a JB5 rear brake drum? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**aotte1** · 07-21-2014, 08:51 PM

Please see attached photo below, is this a JB5 or JB3 rear brake drum?
Les

raulb24 · 07-22-2014, 06:10 PM

looks like JB3 brake drum

Keith Seymore · 07-23-2014, 09:38 AM

If that's off your truck, and your truck was originally a manual brake job, then it's a JB1.

JB3 is the smallest power brake system.

Per the chart JB1 and JB3 use the same drum.

K

**aotte1** · 07-23-2014, 01:13 PM

Thanks, Keith, this not off my red 86 stepper. This is from another 86 chassis I purchased, which has the JB5 front brakes on it, ( however do not think the front suspension is original to that chassis, maybe from Sub). Guess I can remove drum and measure, and my truck is at body shop so can not compare to it's JB3 drums.

Thanks,
Les

Keith Seymore · 07-23-2014, 01:31 PM

Ah - I see.

Yes - you should be able to measure the width of the friction surface/shoes.

JB3 = 2"
JB5 = 2.75"

per the chart.

K

07-21-2014, 08:51 PM	#1
aotte1 Registered User Join Date: Oct 2013 Location: lousiville Ky Posts: 2,645	Is this a JB5 rear brake drum? Please see attached photo below, is this a JB5 or JB3 rear brake drum? Les Attached Images

07-22-2014, 06:10 PM	#2
raulb24 Registered User Join Date: Dec 2010 Location: San Pedro Posts: 19	Re: Is this a JB5 rear brake drum? looks like JB3 brake drum

07-23-2014, 09:38 AM	#3
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,226	Re: Is this a JB5 rear brake drum? If that's off your truck, and your truck was originally a manual brake job, then it's a JB1. JB3 is the smallest power brake system. Per the chart JB1 and JB3 use the same drum. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

07-23-2014, 01:13 PM	#4
aotte1 Registered User Join Date: Oct 2013 Location: lousiville Ky Posts: 2,645	Re: Is this a JB5 rear brake drum? Thanks, Keith, this not off my red 86 stepper. This is from another 86 chassis I purchased, which has the JB5 front brakes on it, ( however do not think the front suspension is original to that chassis, maybe from Sub). Guess I can remove drum and measure, and my truck is at body shop so can not compare to it's JB3 drums. Thanks, Les

07-23-2014, 01:31 PM	#5
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,226	Re: Is this a JB5 rear brake drum? Ah - I see. Yes - you should be able to measure the width of the friction surface/shoes. JB3 = 2" JB5 = 2.75" per the chart. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

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