2 questions need help! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

nickz84 · 02-13-2007, 03:58 AM

hey i have 1979 gmc heavy half i am in need of a brake booster and when I go to parts store there is 2 types jb5 and jb3 and i have no idea which one goes on autozone says it will be un the glove compartment on the tag it isnt there and it isnt under the hood.. how do i find this info out my brakes are almost to the point they dont work at all so immeadiate help would be appreciated.. and also what is the lug pattern on this truck i am looking into buying new rims and i need to know what im lookin at also what the biggest size tire i can put without rubbing.. thanks guys!

boxrodz · 02-13-2007, 04:27 AM

I'm guessin' you have the JB5 system. The JB5 system have the heavy duty rotors ( 1 1/4") vs the JB3 system which have 1" rotors. Measure your rotor thickness to be sure.

Your bolt pattern is 5 on 5. As far as wheel/tire size, is your truck lowered (or do you plan on lowering it)? What size wheels are you planning on running? With the correct backspacing, you can fit a pretty descent wheel/tire combo.

**Captkaos** · 02-13-2007, 12:57 PM

If the 4th position of the VIN is the number 4 this will confirm the heavy half, which by default comes with HD rear suspension and brakes, so you will have the JB5 HD setup. The rear springs are 56" long and have 7 leafs in them.

02-13-2007, 03:58 AM	#1
nickz84 Registered User Join Date: Jun 2006 Location: Las Vegas.Nv Posts: 11	2 questions need help! hey i have 1979 gmc heavy half i am in need of a brake booster and when I go to parts store there is 2 types jb5 and jb3 and i have no idea which one goes on autozone says it will be un the glove compartment on the tag it isnt there and it isnt under the hood.. how do i find this info out my brakes are almost to the point they dont work at all so immeadiate help would be appreciated.. and also what is the lug pattern on this truck i am looking into buying new rims and i need to know what im lookin at also what the biggest size tire i can put without rubbing.. thanks guys!

02-13-2007, 04:27 AM	#2
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: 2 questions need help! I'm guessin' you have the JB5 system. The JB5 system have the heavy duty rotors ( 1 1/4") vs the JB3 system which have 1" rotors. Measure your rotor thickness to be sure. Your bolt pattern is 5 on 5. As far as wheel/tire size, is your truck lowered (or do you plan on lowering it)? What size wheels are you planning on running? With the correct backspacing, you can fit a pretty descent wheel/tire combo. __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... Last edited by boxrodz; 02-13-2007 at 04:49 AM.

02-13-2007, 12:57 PM	#3
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: 2 questions need help! If the 4th position of the VIN is the number 4 this will confirm the heavy half, which by default comes with HD rear suspension and brakes, so you will have the JB5 HD setup. The rear springs are 56" long and have 7 leafs in them. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com



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