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#1 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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72 K2500 Rear Axle Identification.
Hello, Need some help identifying what rear end this is... Looks like a HO52, but not sure the ratio. Its on my 72 K2500 Sierra. I have looked at the identification charts but i don't have any letters in front of the numbers so i am a bit confused. Any help or ideas would be great. Thanks.
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#2 |
Senior Member
![]() Join Date: May 2001
Location: Independence MO.
Posts: 7,697
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Re: 72 K2500 Rear Axle Identification.
There’s a 3 letter code stamped on the top of the 3rd member. If it’s a 70 or older it will be 3 letters.
It’s either 4:10 of 4:57.
__________________
72 3/4t Custom Deluxe 402/auto 66k Original paint 71 3/4t 4x4 Custom Deluxe 10k original miles Original paint 71 3/4t Cheyenne 402 70k original paint 72 3/4t 4x4 Custom deluxe 72 3/4t 4x4 Custom deluxe 91k original paint 72 Cheyenne/30 Dually 69 Camaro SS396 4-speed 13 GMC 2500HD Duramax I bought new 05 Jeep Wrangler "Willys Edition" 12k miles (I bought new) 85 3/4 ton 4x4 Scottsdale 33k miles original paint 86 1 ton 4x4 SRW Silverado 454 restored 80 1 ton 4x4 SRW Silverado 9,434 original miles!! original paint 95 GMC 1 ton dually 4x4 my dad bought new 95 GMC 3/4 ton 4x4, regular cab 454, 31k original miles 2002 2500HD 4x4 regular cab 6.0L 67k miles 2002 2500HD 4x4 regular cab 8.1L 28k miles 2003 GMC 2500HD 4x4 regular cab Diesel 93k miles 67-72 Parts for sale |
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#3 |
All about them K’s
![]() Join Date: Jun 2014
Location: Land of Entrapment
Posts: 6,377
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Re: 72 K2500 Rear Axle Identification.
The engine it came with can help shed some light on it but is not a total guarantee. Small blocks had a standard ratio of 4:11 with the inline 6’s having 4:56 as standard I believe. I’m not sure what the GMC V6’s had for standard. That Might help get you in the ballpark at least.
__________________
Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0 ![]() |
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#4 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
Its has a 350 in it. It must be 4:56 then cause it runs round 3200rpm-3500rpm doing 60MPH down the hwy. Thanks for the info will also check the top of the 3rd member.
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#5 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: 72 K2500 Rear Axle Identification.
Can you post a picture of the SPID (sheet pasted inside the glovebox door)?
What engine was it born with? Does your VIN start with TK"S" or "E" or "M"? All these things can help determine what your truck was born with and what it has now. Keep in mind that your speedo may be way off depending on tire size (use a GPS to determine your rpm at an actual GPS speed). If your truck was born a V8, as Tyler pointed out, your stock ratio would have been 4.10 (in other words, if you still have your SPID, and it has an "E" in the VIN (& 350 appears on your SPID), but NO rear ratio appears on your SPID - your truck was born with 4.10s). But since who knows WHAT someone may have swapped in over the last 49 years - with GPS speed, eng rpm at that speed, and tire diameter, we can tell you precisely what you have now. Look fwd to some pics! We like our K20s around here ![]() |
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#6 |
Registered User
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 7,717
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Re: 72 K2500 Rear Axle Identification.
Unless removed by a PO, the Dana 44 should have a ratio tag under a cover bolt and will match the rear (unless some serious PO stupidity...)
__________________
44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax |
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#7 | |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
Quote:
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#8 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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#9 |
Registered User
![]() Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
Posts: 3,009
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Re: 72 K2500 Rear Axle Identification.
Here is where the rear axle info is stamped on the Eaton third member
__________________
'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 |
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#10 |
All about them K’s
![]() Join Date: Jun 2014
Location: Land of Entrapment
Posts: 6,377
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Re: 72 K2500 Rear Axle Identification.
If it was a small block truck originally and no spid ratio call out, it was born with 4:11’s. Hard to tell what has been done thru the years but probably a reasonable bet it’s got 4:11’s.
__________________
Tyler '57 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=813888 '72 K20 Cheyenne http://67-72chevytrucks.com/vboard/s...d.php?t=662879 ‘69 K10 SWB http://67-72chevytrucks.com/vboard/s...d.php?t=805206 '98 Silverado LT K2500HD ECLB Vortec 454/4l80E: 6" lift 315/75/16's ‘87 IROC-Z all original 50K mile survivor TPI 305 IROC Blue ‘10 Camaro 2SS/RS Aqua Blue Metallic #93 -version 2.0 ![]() |
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#11 |
Registered User
![]() Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
Posts: 3,009
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Re: 72 K2500 Rear Axle Identification.
My book shows 70 and newer the codes are 3 letters and 69 and older are 2 letters.
__________________
'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 |
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#12 |
Carpe manana
![]() ![]() Join Date: Dec 2010
Location: Eau Claire, WI
Posts: 12,383
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Re: 72 K2500 Rear Axle Identification.
It's an Eaton axle but just a clarifying question. Didn't GM use a D60 for K2500s rather than the Ho52 seen with K20s?
__________________
1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 ![]() Last edited by DeadheadNM; 04-05-2021 at 02:48 PM. Reason: added |
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#13 |
Senior Member
![]() Join Date: Apr 2016
Location: Fairbanks, AK
Posts: 336
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Re: 72 K2500 Rear Axle Identification.
My 1972 K2500 has Dana 60 in the rear. Maybe HO52 is a Canadian thing eh?
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1972 GMC K2500 Super Custom Matt |
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#14 |
Registered User
Join Date: Jul 2012
Location: Whitehorse yukon
Posts: 1,218
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Re: 72 K2500 Rear Axle Identification.
I have two k20s both eaton a c20 and c30 d60 diffs
Stock 350 k20 trucks are usually 410 gears both mine have a lockers the other is a straight 6 4.57 gears |
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#15 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
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#16 |
Senior Member
![]() Join Date: May 2001
Location: Independence MO.
Posts: 7,697
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Re: 72 K2500 Rear Axle Identification.
You are correct Pete, I missed the GMC part. I don’t think I have ever seen an HO in a GMC before.
__________________
72 3/4t Custom Deluxe 402/auto 66k Original paint 71 3/4t 4x4 Custom Deluxe 10k original miles Original paint 71 3/4t Cheyenne 402 70k original paint 72 3/4t 4x4 Custom deluxe 72 3/4t 4x4 Custom deluxe 91k original paint 72 Cheyenne/30 Dually 69 Camaro SS396 4-speed 13 GMC 2500HD Duramax I bought new 05 Jeep Wrangler "Willys Edition" 12k miles (I bought new) 85 3/4 ton 4x4 Scottsdale 33k miles original paint 86 1 ton 4x4 SRW Silverado 454 restored 80 1 ton 4x4 SRW Silverado 9,434 original miles!! original paint 95 GMC 1 ton dually 4x4 my dad bought new 95 GMC 3/4 ton 4x4, regular cab 454, 31k original miles 2002 2500HD 4x4 regular cab 6.0L 67k miles 2002 2500HD 4x4 regular cab 8.1L 28k miles 2003 GMC 2500HD 4x4 regular cab Diesel 93k miles 67-72 Parts for sale |
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#17 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
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#18 | |
Registered User
Join Date: Feb 2021
Location: Clifton,Me
Posts: 3
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Re: 72 K2500 Rear Axle Identification.
Quote:
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#19 | |
Registered User
Join Date: Feb 2021
Location: Clifton,Me
Posts: 3
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Re: 72 K2500 Rear Axle Identification.
Quote:
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#20 | |
Senior Member
![]() Join Date: May 2001
Location: Independence MO.
Posts: 7,697
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Re: 72 K2500 Rear Axle Identification.
Quote:
Do you have a picture of your option sticker?
__________________
72 3/4t Custom Deluxe 402/auto 66k Original paint 71 3/4t 4x4 Custom Deluxe 10k original miles Original paint 71 3/4t Cheyenne 402 70k original paint 72 3/4t 4x4 Custom deluxe 72 3/4t 4x4 Custom deluxe 91k original paint 72 Cheyenne/30 Dually 69 Camaro SS396 4-speed 13 GMC 2500HD Duramax I bought new 05 Jeep Wrangler "Willys Edition" 12k miles (I bought new) 85 3/4 ton 4x4 Scottsdale 33k miles original paint 86 1 ton 4x4 SRW Silverado 454 restored 80 1 ton 4x4 SRW Silverado 9,434 original miles!! original paint 95 GMC 1 ton dually 4x4 my dad bought new 95 GMC 3/4 ton 4x4, regular cab 454, 31k original miles 2002 2500HD 4x4 regular cab 6.0L 67k miles 2002 2500HD 4x4 regular cab 8.1L 28k miles 2003 GMC 2500HD 4x4 regular cab Diesel 93k miles 67-72 Parts for sale |
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#21 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
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#22 |
Registered User
![]() Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
Posts: 3,009
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Re: 72 K2500 Rear Axle Identification.
I haven't seen this mentioned yet but have you had the cover off recently? Easy enough to pull the cover, count the gear teeth and you'll have your ratio, a little inspection and fresh oil.
__________________
'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 |
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#23 |
Registered User
![]() Join Date: Mar 2021
Location: Stoon, SK
Posts: 27
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Re: 72 K2500 Rear Axle Identification.
Thanks for all the help. Got the letters off the top of axle. RJH which points to 4:10 gears. Thanks for the tips.
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