The Stovebolt Site Forums The Shop Area Driveline 1947.2-55.1 One Ton Rear End Upgrade - New Tech Tip

What you are describing is an HO72 rear differential that can be swapped with the HO52 . To identify an Eaton 4:10 HO72 - Turn the carrier around where you can see the end of the pinion shaft on the pinion bearing end, the number 3934647 would be stamped there along with the 10-41 number. The stamping may be faint. The ring gear is stamped 3934641 on the flange with bolt holes, below the gear teeth. You may want a flashlight and a mirror to help view the ring gear stamped number.

Ron

Ron - Thanks for the reply, new member here....I want to swap out the 4.57's in my 1948 3600 with a 4.10 unit from a 68-72 C or K20, as described in the article:

https://www.stovebolt.com/techtips/axles/1%20Ton%20Upgrade/

The article states the donor vehicles (3/4 tons) will have an HO52 gear set, but you say I need an HO72 set, can you explain - Thanks

The axle in your truck, if original is an Eaton HO52. In order to perform this tech tip you need to purchase a HO72 rear pumpkin from a salvage yard. Pull the axle shafts and swap the pumpkins. It really is that simple....

Sweet has answered your question. The part numbers I provided are for the pinion and ring gears for an HO72 carrier to help you identify the "pumpkin" you were referring to.

Quoting from the article:

"The desired (for this upgrade) 4.10 ratio is only found in the HO52 axles used 1968-1972 (3/4-ton trucks with the 350/auto trans combo)
To go faster, remove your old HO52 or HO72 center carrier (complete) and replace it with a complete center carrier from a 1968-1972 HO52 axle from a Chevrolet C-20 with a 350/auto trans."

According to this, I need an HO 52, not HO72....

LT 33 - from the same article, at the top, third paragraph - " In fact, this upgrade works for any truck with an Eaton HO52 or HO72 axle (3/4 or 1-ton trucks, 1947 -1972!"
Lets found out what you've found - I suggest you take a look at the carrier you've found and provide at least one part number off the ring gear or the pinion gear and I'll research it for you and provide the information on what you have found. Note, an HO72 carrier ( pumpkin ) will definitely fit your application. Many bolters have made this swap. Suggest you PM John Millman and or Denny Graham, two of the authors, and ask for verification if that will help.

Get me those part numbers.

Ron

Thanks, waiting to hear back from the scrap yard and will let you know

So I have a 58 1-ton dually with 5.14 gears I believe it's a HO72. I also have a 68 3/4 ton 4.10 posi rear end out of a 350/350 truck I believe I have a HO52. I can swap the 3rd member out of the HO72 for the HO52??

Brakes....will I need to find brakes for my HO72 1-ton dually from another newer 14 bolt dually? OR will a SRW 14 bolt brakes work as well??

Reason I ask the brake question is I have a SRW mid 80's 14 bolt 4.10 rear end out of a 3/4 ton.

In my quest to find a gear set to replace the HO72/5:14s I MAY have struck gold? Found a '70 3/4 ton with coil sprgs. but when I looked in the cab my heart sunk, it had a manual trans. Eng is gone but it appears to have been a small block. I've read that some coil versions could be 4:10. Does anyone have any experience on the subject? Thanks

Pick1, Check the glove box door for a decal with the build codes of the truck. One of those should ID the axle installed. If you can take a pic and post, folks here may be able to help decide the sticker to ID the axle in question.

Gdads51, I'll have to return in the spring. The wrecking yard currently has a nice layer of white stuff ( yep, even in AZ) plus the owner has his hands full running a towing business. Thanks