72 K2500 Rear Axle Identification. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

FishEyes · 04-04-2021, 02:19 PM

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.

**Joesjunk** · 04-04-2021, 05:10 PM

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.

57taskforce · 04-04-2021, 06:24 PM

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.

FishEyes · 04-04-2021, 07:01 PM

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.

**jocko** · 04-04-2021, 09:41 PM

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

Mike C · 04-04-2021, 11:22 PM

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...)

FishEyes · 04-05-2021, 09:16 AM

Quote:

Originally Posted by jocko

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

The SPID doesn't have the gear ratio on it. It is a TKE, and the tires are 265 75 R16. I will do the GPS test when i get home on Wednesday, and get some pics up Wed eve. Thanks again.

FishEyes · 04-05-2021, 09:18 AM

Quote:

Originally Posted by Mike C

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...)

Great idea never thought of that.

**MJN** · 04-05-2021, 09:33 AM

Here is where the rear axle info is stamped on the Eaton third member

57taskforce · 04-05-2021, 01:06 PM

Quote:

Originally Posted by FishEyes

The SPID doesn't have the gear ratio on it. It is a TKE, and the tires are 265 75 R16. I will do the GPS test when i get home on Wednesday, and get some pics up Wed eve. Thanks again.

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.

**MJN** · 04-05-2021, 01:33 PM

Quote:

Originally Posted by Joesjunk

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.

My book shows 70 and newer the codes are 3 letters and 69 and older are 2 letters.

**DeadheadNM** · 04-05-2021, 02:30 PM

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?

**Fbks_Cruiser** · 04-05-2021, 04:32 PM

My 1972 K2500 has Dana 60 in the rear. Maybe HO52 is a Canadian thing eh?

gmc684x4 · 04-05-2021, 05:38 PM

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

FishEyes · 04-05-2021, 06:36 PM

Quote:

Originally Posted by Fbks_Cruiser

My 1972 K2500 has Dana 60 in the rear. Maybe HO52 is a Canadian thing eh?

LOL, the ol girl was born in Fremont, CA.

**Joesjunk** · 04-05-2021, 10:25 PM

Quote:

Originally Posted by DeadheadNM

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?

You are correct Pete, I missed the GMC part. I don’t think I have ever seen an HO in a GMC before.

FishEyes · 04-05-2021, 11:53 PM

Quote:

Originally Posted by Joesjunk

You are correct Pete, I missed the GMC part. I don’t think I have ever seen an HO in a GMC before.

So the Dana 60 rear end was how the K 2500 came from the factory?

71250 · 04-06-2021, 06:52 AM

Quote:

Originally Posted by 57taskforce

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.

Not to hijack the thread.. but I have 71 250, so I’m guessing the ratio is a 4:56?

71250 · 04-06-2021, 07:10 AM

Quote:

Originally Posted by 57taskforce

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.

Not to hijack the thread.. but I have 71 250, so I’m guessing the ratio is a 4:56?

**Joesjunk** · 04-06-2021, 08:42 AM

Quote:

Originally Posted by FishEyes

So the Dana 60 rear end was how the K 2500 came from the factory?

To the best of my knowledge GMC K trucks had Dana 60 rear axles and the Chevy had the Eaton.

Do you have a picture of your option sticker?

FishEyes · 04-06-2021, 08:58 AM

Quote:

Originally Posted by Joesjunk

To the best of my knowledge GMC K trucks had Dana 60 rear axles and the Chevy had the Eaton.

Do you have a picture of your option sticker?

I will get a pic put up tomorrow. There is not any axle info on the sticker thought. Thanks

**MJN** · 04-06-2021, 03:08 PM

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.

FishEyes · 04-08-2021, 03:41 PM

Thanks for all the help. Got the letters off the top of axle. RJH which points to 4:10 gears. Thanks for the tips.

04-04-2021, 02:19 PM	#1
FishEyes Registered User Join Date: Mar 2021 Location: Stoon, SK Posts: 27	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. Attached Images

04-04-2021, 05:10 PM	#2
Joesjunk Senior Member Join Date: May 2001 Location: Independence MO. Posts: 7,689	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

04-04-2021, 06:24 PM	#3
57taskforce All about them K’s Join Date: Jun 2014 Location: Farmington, New Mexico Posts: 6,238	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

04-04-2021, 07:01 PM	#4
FishEyes Registered User Join Date: Mar 2021 Location: Stoon, SK Posts: 27	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.

04-04-2021, 09:41 PM	#5
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,937	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

04-04-2021, 11:22 PM	#6
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,714	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

04-05-2021, 09:33 AM	#9
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 2,967	Re: 72 K2500 Rear Axle Identification. Here is where the rear axle info is stamped on the Eaton third member Attached Images __________________ '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

04-05-2021, 02:30 PM	#12
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,297	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 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland Last edited by DeadheadNM; 04-05-2021 at 02:48 PM. Reason: added

04-05-2021, 04:32 PM	#13
Fbks_Cruiser Senior Member Join Date: Apr 2016 Location: Fairbanks, AK Posts: 329	Re: 72 K2500 Rear Axle Identification. My 1972 K2500 has Dana 60 in the rear. Maybe HO52 is a Canadian thing eh? __________________ 1972 GMC K2500 Super Custom Matt

04-05-2021, 05:38 PM	#14
gmc684x4 Registered User Join Date: Jul 2012 Location: Whitehorse yukon Posts: 1,218	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

04-06-2021, 03:08 PM	#22
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 2,967	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

04-08-2021, 03:41 PM	#23
FishEyes Registered User Join Date: Mar 2021 Location: Stoon, SK Posts: 27	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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