Rear End - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70short · 01-14-2011, 11:34 AM

I have A "70" with 6 lug axles 308. Found one for sale out of A "72" auto truck for sale I am going to look at. Aren't the auto trucks 373 gears and are they not A narrower rear end? How much narrower? Is the swap over to narrower when they went from 6 lug to 5 lug?

brn agn · 01-14-2011, 01:14 PM

I'm not sure about the gear ratio, but the 71 and 72 12 bolt rear ends are approximately 1.5" WIDER than the 67-70 rear ends. I believe that this coincides with the 6 lug to 5 lug switchover. Hopefully someone else will confirm.

VDOG · 01-14-2011, 03:17 PM

I can only tell you 1970 and later rearends are different from 69 on down.
Found out the hard way when I took a 3:73 rearend out of a 71 6 cyl truck to put in my 69.

Once installed, the the passenger side axle went in deeper than the driver
side. 70 and up one axle is shorter than the other.

treveiger · 01-14-2011, 04:01 PM

So you cant swap a 71 rearend into a 69 chevy truck?

Longhorn Man · 01-14-2011, 10:29 PM

67 to early 70 were narrow, mid 70 - 72 were wider by 3/4 inch on BOTH sides.
no 3.08 gears stock in 67 - 72, that was a car gear back then. The 3.07 gear was the standard gear in most non big block automatic and 4 speed 1/2 ton trucks. The 3.73 gear was the standard gearset in most 3 speed 1/2 ton trucks. There were exceptions in certian years with certian engines, but that is the generic rule on gearing.

70short · 01-18-2011, 03:34 AM

So is it safe to say that my 6 lug "70" is the narrow rear end since its 6 lug??

Gary

Longhorn Man · 01-18-2011, 06:42 AM

actually no. The odds are more likely to be yhat it is the longer one. The wide rear seems way more common over the narrow one.

01-14-2011, 11:34 AM	#1
70short Registered User Join Date: Sep 2003 Location: Boise ID Posts: 609	Rear End I have A "70" with 6 lug axles 308. Found one for sale out of A "72" auto truck for sale I am going to look at. Aren't the auto trucks 373 gears and are they not A narrower rear end? How much narrower? Is the swap over to narrower when they went from 6 lug to 5 lug? __________________ "72" Red CORVETTE 4-speed 350 "70" Chevy Short Bed early stages of resto. Edel 600 cfm carb Weiand Stealth Intake HEI shorty Headers 4/2 Drop 295 50R 15 TOYO on 10 inch wide corvette rally rims at all 4 corners. "CHEVY RULES"

01-14-2011, 01:14 PM	#2
brn agn Registered User Join Date: Mar 2009 Location: Youngsville, NC Posts: 952	Re: Rear End I'm not sure about the gear ratio, but the 71 and 72 12 bolt rear ends are approximately 1.5" WIDER than the 67-70 rear ends. I believe that this coincides with the 6 lug to 5 lug switchover. Hopefully someone else will confirm. __________________ 1969 C10 SWB Project Charity Case AKA "Roscoe" 1971 Cheyenne Super A Combined Effort The Service Station-A practical ministry for those in need

01-14-2011, 03:17 PM	#3
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Re: Rear End I can only tell you 1970 and later rearends are different from 69 on down. Found out the hard way when I took a 3:73 rearend out of a 71 6 cyl truck to put in my 69. Once installed, the the passenger side axle went in deeper than the driver side. 70 and up one axle is shorter than the other.

01-14-2011, 04:01 PM	#4
treveiger Senior Member Join Date: Jul 2010 Location: South Dakota Posts: 4,093	Re: Rear End So you cant swap a 71 rearend into a 69 chevy truck? __________________ 1969 Chevy c20(Miss Hackjob)

01-14-2011, 10:29 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Rear End 67 to early 70 were narrow, mid 70 - 72 were wider by 3/4 inch on BOTH sides. no 3.08 gears stock in 67 - 72, that was a car gear back then. The 3.07 gear was the standard gear in most non big block automatic and 4 speed 1/2 ton trucks. The 3.73 gear was the standard gearset in most 3 speed 1/2 ton trucks. There were exceptions in certian years with certian engines, but that is the generic rule on gearing.

01-18-2011, 03:34 AM	#6
70short Registered User Join Date: Sep 2003 Location: Boise ID Posts: 609	Re: Rear End So is it safe to say that my 6 lug "70" is the narrow rear end since its 6 lug?? Gary __________________ "72" Red CORVETTE 4-speed 350 "70" Chevy Short Bed early stages of resto. Edel 600 cfm carb Weiand Stealth Intake HEI shorty Headers 4/2 Drop 295 50R 15 TOYO on 10 inch wide corvette rally rims at all 4 corners. "CHEVY RULES"

01-18-2011, 06:42 AM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Rear End actually no. The odds are more likely to be yhat it is the longer one. The wide rear seems way more common over the narrow one.



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