The Stovebolt Site Forums The Shop Area Engine Shop Another rear end question or 2.

In my quest to find better gearing for my '57 3800, I've located a rear axle from a '70 C30 that the owner claims to be an Eaton limited slip with 4.10 ratio. My first question is will this axle be a direct bolt-in for my '57? Next, I'm a little confused about what this axle really is. My limited knowledge of this tells me that an Eaton axle under a C30 would be an HO72. The info I've read about these says that the HO72 was never available with 4.10 gears. He's 4 hours away so I don't want to make the trip and find out it's soemthing that I can't use. Can anyoue out there provide some insight on this? I've asked him to e-mail some pix but don't have them yet. Thanks for any help you can provide.

Hi. I installed an Eaton HO72 with 4.10 gears and "No-Spin" in my 1949 Chevy 3600 3/4-ton. I understand the Eaton HO52 and HO72 are identical except that the HO72 also has a thrust bearing adjustment(?). I'm not familiar with the '57 trucks, but if it's an Eaton HO52/72, you should have no problem.

If nothing else, the "No-Spin" option on the Eaton rearend is worth the risk. All of the 4x4 guys on the '67 to '72 Chevy Trucks web site are looking for the "No Spin" opion.

Good Luck!
Dan M.

I'd be tempted to just make the trip. Its going to be real hard to know the gear ratio short of checking it on the spot.

The HO numbers refer to the axle as a whole, and reflect the weight rating of the axles. The biggest difference between the two axles is the size of the brakes, followed by the standard gear ratios. The differentials easily swap.

The No-Spin is desirable, but may not be for your application.

As the others have noted, the Eaton parts will swap no problem. Before you make a 4 hour trip, though, see if the seller can give you the ID code off the center cection. That will tell you if it's a 4.10 or not. The codes for a 4.10 HO72 rear for 1970 are as follows, TIE, TIH, TJL, TLX, TLZ, TMR, TNZ, TRN. There is also a possibility that it might be a Spicer 70, which was also common in the 1 tons of that era, though that is more of a GMC application. Even if it is a Spicer, you could swap the entire rear if you wanted to get the gearing.

I made the trip and think I came out okay. Here's the truck that's being parted. http://67-72chevytrucks.com/vboard/showthread.php?t=364393
I got the rear axle and the 9' stepside bed (minus fire equipment). The axle is a 4.10 Detroit locker and the truck only has 12,000 miles on it. I plan to put both the axle and bed on my '57 3800.