Gear ratio question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**MJN** · 02-09-2005, 04:47 PM

Ok, I found a '71 GMC c/1500 in the junkyard up here. On the option sheet is listed a posi rear end but no gear ratio is listed. It is a leaf sprung rear axle, 5 lug 12 bolt. Now does this mean it's got 3.08's in it since it's not listed on the option sheet and they were the standard gear set?

**CPNE** · 02-09-2005, 05:08 PM

Depends on engine/tranny. For 1/2 tons a V8 auto is usually 3:08, an I6 manual is usually 3:73. 4:11's were an option in 1/2 tons, but never standard with any drivetrain combo IIRC

**MJN** · 02-09-2005, 06:08 PM

it's got a v-8 (not listed on option sheet) and a 3-speed manual.

Blazer1970 · 02-09-2005, 07:21 PM

350 V-8 came with 3.07s. 307 V-8 or 6 cylinder came with 3.73s.

Longhorn Man · 02-09-2005, 10:32 PM

Since no option for engine is listed, and asuming it is a CE vin truck (first two digits of the vin) then it'll be a 307. With the 3 speed it would be a 3.73. All my books say there were no 3.07 posi rears...but everyone seems to find them so hell, they probably do exist.

**MJN** · 02-10-2005, 12:19 AM

I've got a 3.08 posi in my Blazer but I was just wondering about this GMC in the junkyard and if it's worth grabbing. Since it's a factory posi.

02-09-2005, 04:47 PM	#1
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 3,015	Gear ratio question Ok, I found a '71 GMC c/1500 in the junkyard up here. On the option sheet is listed a posi rear end but no gear ratio is listed. It is a leaf sprung rear axle, 5 lug 12 bolt. Now does this mean it's got 3.08's in it since it's not listed on the option sheet and they were the standard gear set? __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com

02-09-2005, 05:08 PM	#2
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,664	Depends on engine/tranny. For 1/2 tons a V8 auto is usually 3:08, an I6 manual is usually 3:73. 4:11's were an option in 1/2 tons, but never standard with any drivetrain combo IIRC __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

02-09-2005, 07:21 PM	#4
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	350 V-8 came with 3.07s. 307 V-8 or 6 cylinder came with 3.73s. __________________ Tim

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02-09-2005, 06:08 PM	#3
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 3,015	it's got a v-8 (not listed on option sheet) and a 3-speed manual.

02-09-2005, 10:32 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Since no option for engine is listed, and asuming it is a CE vin truck (first two digits of the vin) then it'll be a 307. With the 3 speed it would be a 3.73. All my books say there were no 3.07 posi rears...but everyone seems to find them so hell, they probably do exist.

02-10-2005, 12:19 AM	#6
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 3,015	I've got a 3.08 posi in my Blazer but I was just wondering about this GMC in the junkyard and if it's worth grabbing. Since it's a factory posi.



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