The Stovebolt Site Forums The Shop Area Driveline Recognize this rear end?

This is what was under my 53 3600 frame. Yes it is upside down. 10 Bolt, evenly spaced except for 2 on each side which are closer together. Is this the standard rear-end?

53 3600 RE

It looks right- - - - -does the differential assembly bolt in from the front with a similar bolt circle? If so, it's probably the HO52 which is standard for 3/4 and 1 ton axles, with only a difference in the hubs and brakes. There should be an adjusting bolt and a locknut on the driver's side of the differential assembly which moves a thrust plate against the ring gear.
Jerry

Someone will correct me if I'm mistaken but the ho52 and ho72 are almost identical externally.ho52 was the 3/4ton and ho72 was the 1 ton axle. The 72 has the thrust adjustment on side of case. Not sure if the 52 also had this. As a side note. If you take the cover off and find the 5.14/1. Ratio gears its probably a Ho72

The HO 72 is a MUCH later model of that rear end, like mid-1960's. The HO 52 goes back into the late 1940's-early 50's. The entire center section will interchange, but individual internal components are very different. Some of the 72's were also offered with a Detroit Locker limited slip option.
Jerry

Allen, it probably has the 4.56 gears. Unless you want to stay totally original, you might want to consider switching to 4.10 gears. As mentioned above, the center section is an easy, direct swap out. It is a particularly easy swap with the rear end out of the truck because you don't have to do it laying on your back! The 4.10 will give you much better gearing for today's roads.

There is one for sale in the swap meet forum.

If you want to look for one locally, keep your eyes open for 1967 to 1972 C20's and C30's with V8's and automatics.

Matt

I beg to differ but I have a 49 gmc with a ho72. And my 49 gmc manual states that what it should be

OK, go ahead and differ.
Jerry

Lol. God knows it wouldn't be my first mistake!!

Eaton HO52 or HO72 axle (3/4 or 1-ton trucks, 1947 -1972!)

from: Tech Tip

Thanks fellas. I thought I had added some shots of the front section and hubs. I have now put them in the link, and the front does follow your description Jerry.

Matt, I'll check, but factory specs indicate a 4.57 RE. Is 4.11 the lowest I should go (as in John's tech tip - thanks Tim) or could I put in 3.55? See the link below.

Re Gear Swap

Allen, the tallest gears for the Eaton HO52 are the 4.10's. The 3.55's and 3.38's that are out there from aftermarket vendors won't fit.

Matt

Thanks Matt. What's the easiest way to not get snookered at the swap meet without taking the RE with me. Is there a series of numbers or can I take some small parts with me?

The ring gear will be stamped 10-41 on a 4.10. It is easy to see. But that assumes the pumpkin has been removed.

It it is still on the rear end, you can to a rough check by jacking up one or both of the rear wheels. You'll want to check for two things. First, check to see if it is an open differential or if it has the Detroit Locker. Once you know if it is a locker or not, you can turn one tire while counting the rotations of the driveshaft. The calculation is different if it is an open driveshaft or a locker. If you do a search, you'll easily find the details of how to do this.

If you find a 4.10 with a locker, you hit the jackpot! If you find a locker without the 4.10, consider buying the locker anyway because they are hard to find and expensive. You can add it to your 4.10 center section when you find one.

The problem with checking it by turning a tire is that the 4.56 and 4.10 ratios are close enough that it is hard to determine exactly which one it is based on driveshaft turns. It gives you an estimate. Since you already have a 4.56, experiment with it to know what you are working with. That way, if you see a different result when looking at another rear end, it will be more apparent. Still check the ring gear when you pull it just to be sure.

Good luck,

Matt

If it cannot be turned with only one end of the axle in the air, it is a locker, lockers require both ends in the air to be turned.

Ed