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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Oct 2004 Posts: 1,780 Master Gabster | | Master Gabster Joined: Oct 2004 Posts: 1,780 | I consolidated information regarding the conversion of the 1947/55 3600 & 3800 rear ends. This information will help you change the gear ratio to 4:10 from the original lower gears.
AXLE IDENTIFICATION
denny graham how-to photo's
This information should be helpful to those that are looking for the eatons.
From Bill: (Longbox55):
There will be a code stamped on the front face of the carrier. I've posted the codes before, but for sake of saving a ton of searching for them, here they are again:
1967; HW, JU. These are listed as 4.11, may be Spicer rather than Eaton
1968; NA, NB, WI, RN (RN is listed as a 1 ton diff)
1969; NA, NB, OT, OW, OY, TF. There are also 1 ton listings; IE, LJ, LZ, MR, NZ, RN.
1970; TAA, THU, THW, TJU, TLN, TMZ, TNA, TNB, TOT, TTF, TWI.
1 ton; TIE, TIH, TLJ, TLX, TLZ, TMR, TNZ,TRN.
4x4 K20; TPW, TPX
1971; TAH, TAJ, TJA,TJB, TJP, TJS, 2G.
1 ton; TAK, TAL, TAP, TJK, TPZ.
4x4; TJH, TJJ,TKB, TKC, TKK, TKL, TKS, TKT.
1972; RAH, RAJ, RJA, RJB, RKK, RKL, RKS, RKT, RJP, RJS, RKB, RKC.
1 ton; RAK, RAL, RAK, RAP, RJK.
4x4; RJH, RJJ.
I do have listings for a 3.54 ('71 and '72) and a 4.11 ('67-'72). but from what I understand, those are Spicer differentials rather than Eaton, though I have seen a '72 with a 3.54 code on an Eaton differential.
BTW, most, if not all, GMC trucks from the '60s used a Spicer differential in the rear, either a Spicer 60 or 70 (I've seen them both ways).
_________________________ | | | | | Joined: Sep 2002 Posts: 467 'Bolter | | 'Bolter Joined: Sep 2002 Posts: 467 | Get them to look at the gear stampings if possible! The casting number on the carrier is only accurate if the original gears are still in there...mine weren't! | | | | | Joined: Jul 2012 Posts: 14 New Guy | | New Guy Joined: Jul 2012 Posts: 14 | Thank you for info. i am sure it will come in handy when i tear into it shortly,a little bite of luck it does the two piece drive shaft with U joints at the rear end.I have had this truck for i think 32 years and ready to get it going again,I get most of my parts through CHEVY DUTY in KANSAS CITY. | | | | | Joined: Dec 2004 Posts: 1,897 Shop Shark | | Shop Shark Joined: Dec 2004 Posts: 1,897 | George, will this work on the 55.2-72 trucks with an eaton rear as well? I don't have one, so this is more a question out of curiosity than necessity. | | | | | Joined: Oct 2007 Posts: 725 Shop Shark | | Shop Shark Joined: Oct 2007 Posts: 725 | I have never seen a DANA/Spicer diff under a '67-'72 Chevy truck, unless it has been changed, something I have considered because of the various ratios available. Every single truck that I have personally seen has an Eaton axle/diff. In reading other forums, I have seen mention of a 3.90 gear set for the Eatons, but it seems to be nothing but "rear end vaporware!" It may be that the assembly plants out West used one rear end while those in the East used another for shipping reasons or whatever. I'd love to find a DANA/Spicer 60 for my truck because a local supply house has gear sets on the shelf. It is my HO52 Eaton that I can't find anything taller than 4.11 for. Go figure!
Best wishes,
Les | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | The Dana/Spicer was generally used under Chevrolets with the leaf spring option (3/4 ton), many of which were either Camper Specials or Longhorns.
Bill Burmeister
| | | | | Joined: Jun 2009 Posts: 79 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2009 Posts: 79 | The dana/ spicer were primarly used by GMC while 3/4 & 1ton Chevy trucks (usually) ran the Eaton regardless of what it had for a suspension, but prehaps with the exception of the optional 4.11 ratios. All of the GMC trucks from the 60's and early 70's that I have seen with the Eaton rear were 10K GVW trucks with the 5.14 ratios. | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | Perhaps I should rephrase waht I posted. What I meant was that the Dana/Spicer rearend was commonly used with the leaf spring option on the 3/4 ton, not so much that the leaf spring option andated the Dana/Spicer rear. That said, though, virtually all leaf spring 3/4 tons and Camper specials I've seen had the Dana rear. I've seen Longhorns and 1 ton Chevrolets both ways.
Bill Burmeister
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