Diff Identification/Gear Ratio Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Bryce80 · 07-11-2018, 05:35 PM

Purchased a 1972 K20, digging in to find information on the rear end. Looking for any help on identification. Believe its an eaton, ratio unsure, locked unsure, etc. Been looking for identification with the numbers stamped on the front of the rear diff. Any help?

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weq92f · 07-11-2018, 06:30 PM

May or may not be correct but...

Looks like that number identifies the carrier.

Have a look at this link:

https://www.venturestruckparts.com/p...ier-ho72-ho52/

...and search for your casting number.

Have a look at this thread:

http://67-72chevytrucks.com/vboard/s...ad.php?t=25777

-klb

**LockDoc** · 07-11-2018, 07:09 PM

-
This thread I posted back in 2013 might help. See post #8 and #19 for a couple of the code locations used.

http://67-72chevytrucks.com/vboard/s...d.php?t=578793

LockDoc

Killer Bee · 07-11-2018, 09:38 PM

of course, opening it up is most accurate way to determine ratio, locker, etc..

but some external clues may clear up some of it and identify what it was at assembly time..

this thread has some info on Eaton HO52/72
https://www.stovebolt.com/techtips/a...Ton%20Upgrade/

there's a picture in that article of a 'locker tag' that I found on one of mine..

but note, the presence of the tag is the tell, the tag has no stamps or writing on it..

I found a date and ratio stamped in the ring gear..

Bryce80 · 07-11-2018, 10:15 PM

Thank you for the info.

Mike C · 07-12-2018, 05:16 PM

Dana put a tag on all of their diffs that show the gear ratio. So unless someone has removed the tag check your front differential cover. The front and rear must match on a 4 wheel drive, at least closely. For instance if you have 4.10 in the rear the Dana may have 4.09 in the front.

So look for the tag under one of the cover bolts and that should answer the question about what the rear ratio is.

Killer Bee · 07-12-2018, 06:41 PM

^ great point! that's how I quick checked my K20 and K1500

71 K20 HD44 front

72 K1500 D44 front

07-11-2018, 06:30 PM	#2
weq92f Registered User Join Date: Oct 2016 Location: Dallas Texas Posts: 2,881	Re: Diff Identification/Gear Ratio Help May or may not be correct but... Looks like that number identifies the carrier. Have a look at this link: https://www.venturestruckparts.com/p...ier-ho72-ho52/ ...and search for your casting number. Have a look at this thread: http://67-72chevytrucks.com/vboard/s...ad.php?t=25777 -klb __________________ 67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold Last edited by weq92f; 07-11-2018 at 06:36 PM.

07-11-2018, 07:09 PM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,332	Re: Diff Identification/Gear Ratio Help - This thread I posted back in 2013 might help. See post #8 and #19 for a couple of the code locations used. http://67-72chevytrucks.com/vboard/s...d.php?t=578793 LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

07-11-2018, 09:38 PM	#4
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,729	Re: Diff Identification/Gear Ratio Help of course, opening it up is most accurate way to determine ratio, locker, etc.. but some external clues may clear up some of it and identify what it was at assembly time.. this thread has some info on Eaton HO52/72 https://www.stovebolt.com/techtips/a...Ton%20Upgrade/ there's a picture in that article of a 'locker tag' that I found on one of mine.. but note, the presence of the tag is the tell, the tag has no stamps or writing on it.. I found a date and ratio stamped in the ring gear.. __________________ *I started out with nothing - and I still have most of it*

07-11-2018, 10:15 PM	#5
Bryce80 Registered User Join Date: Jul 2018 Location: Foresthill, Ca Posts: 3	Re: Diff Identification/Gear Ratio Help Thank you for the info.

07-12-2018, 05:16 PM	#6
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,712	Re: Diff Identification/Gear Ratio Help Dana put a tag on all of their diffs that show the gear ratio. So unless someone has removed the tag check your front differential cover. The front and rear must match on a 4 wheel drive, at least closely. For instance if you have 4.10 in the rear the Dana may have 4.09 in the front. So look for the tag under one of the cover bolts and that should answer the question about what the rear ratio is. __________________ 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

07-11-2018, 05:35 PM	#1
Bryce80 Registered User Join Date: Jul 2018 Location: Foresthill, Ca Posts: 3	Diff Identification/Gear Ratio Help Purchased a 1972 K20, digging in to find information on the rear end. Looking for any help on identification. Believe its an eaton, ratio unsure, locked unsure, etc. Been looking for identification with the numbers stamped on the front of the rear diff. Any help?

07-12-2018, 06:41 PM	#7
Killer Bee Registered User Join Date: Jan 2016 Location: Barber City, CA Posts: 4,729	Re: Diff Identification/Gear Ratio Help ^ great point! that's how I quick checked my K20 and K1500 71 K20 HD44 front 72 K1500 D44 front __________________ *I started out with nothing - and I still have most of it*



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