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

**Already Gone** · 06-22-2016, 02:30 PM

Does anyone know what the stock rear end ratio is on a 1973 C20 Burb with a 454 and TH400 trans.? The Burb has factory A/C and posi traction as a spid option. There is no trailer tow package option on the spid. I'm hoping for a 3:54 like the 72's had.

Ski-me · 06-22-2016, 05:10 PM

What does your glove box say for an RPO code?

GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)

**Already Gone** · 06-22-2016, 05:50 PM

Thanks for the reply. I don't know when GM starting using the black and white RPO labels but I think in the later 70's. attached are a pic of the spid and the window sticker. The Birb is for sale and I'm thinking of buying it but am not a friend of 4:10s with a 454.

BLOWN73 · 06-22-2016, 06:07 PM

1/2 ton or 3/4 ton?

**Already Gone** · 06-22-2016, 06:17 PM

Quote:

Originally Posted by BLOWN73

1/2 ton or 3/4 ton?

Its a 3/4 ton

BLOWN73 · 06-22-2016, 06:20 PM

I'd be looking in the 3.00-3.50 range

3QTRTONS · 06-22-2016, 06:41 PM

According to:

https://www.gmheritagecenter.com/doc...t-Suburban.pdf

3.73 was stock, with 3.21 or 4.10 as optional ratios. I highly doubt 3.21 with the RPO trailer package; would seriously believe that its 4.10........ jmo

3QTRTONS · 06-22-2016, 07:18 PM

The 3.54 you refer to for '72 was an L47 option (not RPO) - they were ONLY available on CE20 Burbs with 400 sbc.
Those gears were in a "Dana 5500" rear axle. Hen's teeth.

My '72 K20 has 4.10 gears; Eaton HO52 rear & Dana 44 front.

You always could switch out the gear if it is 4.10 and not 3.73 -jessayin'

06-22-2016, 02:30 PM	#1
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,073	Rear End Ratio Question Does anyone know what the stock rear end ratio is on a 1973 C20 Burb with a 454 and TH400 trans.? The Burb has factory A/C and posi traction as a spid option. There is no trailer tow package option on the spid. I'm hoping for a 3:54 like the 72's had. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

06-22-2016, 05:10 PM	#2
Ski-me Registered User Join Date: May 2012 Location: Colo Springs, CO Posts: 870	Re: Rear End Ratio Question What does your glove box say for an RPO code? GQ1 -- AXLE REAR, STD RATIO GT4 -- AXLE REAR, 3.73 RATIO GT5 -- AXLE REAR, 4.10 RATIO GU4 -- AXLE REAR, 3.08 RATIO GU5 -- AXLE REAR, 3.23 RATIO GU6 -- AXLE REAR, 3.42 RATIO G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION) __________________ - Jeff 89' K5 Blazer, 2.5" lift, 35" tires 04' GMC Yukon XL, 3/4 ton, 8.1L

06-22-2016, 05:50 PM	#3
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,073	Re: Rear End Ratio Question Thanks for the reply. I don't know when GM starting using the black and white RPO labels but I think in the later 70's. attached are a pic of the spid and the window sticker. The Birb is for sale and I'm thinking of buying it but am not a friend of 4:10s with a 454. Attached Images __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

06-22-2016, 06:07 PM	#4
BLOWN73 Registered User Join Date: Jul 2009 Location: visalia, ca Posts: 110	Re: Rear End Ratio Question 1/2 ton or 3/4 ton?

06-22-2016, 06:20 PM	#6
BLOWN73 Registered User Join Date: Jul 2009 Location: visalia, ca Posts: 110	Re: Rear End Ratio Question I'd be looking in the 3.00-3.50 range

06-22-2016, 06:41 PM	#7
3QTRTONS Registered User Join Date: Mar 2010 Location: Warren, ME. Posts: 233	Re: Rear End Ratio Question According to: https://www.gmheritagecenter.com/doc...t-Suburban.pdf 3.73 was stock, with 3.21 or 4.10 as optional ratios. I highly doubt 3.21 with the RPO trailer package; would seriously believe that its 4.10........ jmo __________________ 1994 C1500 rclb 1988 C1500 rclb 1969 ES5500 B E A S T 1983 C10 'farm truck' 1976 K20 Suburban 1984 K10 Suburban 1981 Jeep CJ5/350 Vortec 1941 Dodge WC18 Ambulance 2000 GMC Bus (parts warehouse)

06-22-2016, 07:18 PM	#8
3QTRTONS Registered User Join Date: Mar 2010 Location: Warren, ME. Posts: 233	Re: Rear End Ratio Question The 3.54 you refer to for '72 was an L47 option (not RPO) - they were ONLY available on CE20 Burbs with 400 sbc. Those gears were in a "Dana 5500" rear axle. Hen's teeth. My '72 K20 has 4.10 gears; Eaton HO52 rear & Dana 44 front. You always could switch out the gear if it is 4.10 and not 3.73 -jessayin' __________________ 1994 C1500 rclb 1988 C1500 rclb 1969 ES5500 B E A S T 1983 C10 'farm truck' 1976 K20 Suburban 1984 K10 Suburban 1981 Jeep CJ5/350 Vortec 1941 Dodge WC18 Ambulance 2000 GMC Bus (parts warehouse)



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