The Stovebolt Site Forums The Shop Area Driveline Quick Differential swap question

O.k., so i've finally located an Eaton HO72 differential so i can swap it out with mine in my 54 3/4 ton. I have the 4.57 gears. As i understood it the 67-72 Eaton H052-72's for 3/4 tons either had 4.10 or 4.57 gears. This guy thought it had 4.10 gears but upon looking closer it has 4.11 gears. After looking it up i think the 1 ton HO72's came with 4.11 gears. Would this still work in my 3/4 ton as an easy Differential swap? and if so would i still gain nearly as much cruising speed?

Thanks for the input.

Hy gtreasur, yes you will gain top speed.

3B, The 1 ton will work in my 3/4 though?

Yes, it will work fine. The main difference between them are in the brakes. The only part you'll actually need to use is the 3rd member itself, swapped into the existing housing on your truck.

Thanks guys.

How did you determine that is was 4.11? I would have expected 4.10, that is 41/10 tooth ratio.

Truckernix,

He checked and said they were 37/9, which would be 4.11. I don't know anything about these, only what i've been told and what i've found on line. I did find on line that the 1 ton eaton HO72's did come with a 4.11 gear ratio. Have you ever heard of 4.11's in them?

The reason why I commented was that 4.11 was the radio in the later 1/2 Tons. I was under the impression the the HO72 was 4.10, I know mine is.

Ah, It is an 8 lug, so i figure it has to either br 3/4 or 1 ton. The hard thing trying to find one that will work is that nobody selling them usually is sure what it is because they bought it second hand or it's been laying in the back yard for years, lol.

There is another type of rearend used in those years, I think it was maybe a Dana and it is not a front loader. Of course, it would be incompatible.

Yes, i do not believe it is a Dana.

If it's a 3rd member type it's not spicer / dana.

He said it was a 3rd member type, guess i'll find out for sure Saturday.

HeavyChevy, has 3.90 gears for the 62-72's. There won't be much of a difference over the 4.10, but it'll be quite significant over the 4.57's.

Thanks Whitedog, I'll keep that in mind in case i need a little more top end.

swapped out my differential this weekend, all went smooth....i think. replaced my stock 4.57 with an Eaton with 4.11 gears. It looked to be in great shape. The owner said he was just driving the truck last week that it came out of. The swap could not have been easier, slid right in. Berfore i put it in i chacked to make sure it was turning freely. After i put it in i slid the axle shafts back in and before i bolted them down i turned one and the yoke was turning as it should. Then i attached the drive shaft back and was then able to turn the axle shaft freely as before. That didn't seem right to me, is it? The truck was left in gear with the tires blocked. Could it be that i hadn't filled it with oil yet?

I don't quite understand. Did the axles go in flush with the hub?

Yes, they went in flush just as they are suppossed to.

I guess i didn't explain very well, Before i attached the drive shaft to the yoke and bolted the axle shafts in place ( i slid them in all the way, just not bolted down) I turned the axle shafts to make sure the yoke was turning as it should...it was. So then i attached the draive shaft and tried turning the axle shaft again beforte i put the bolts in it, and the yoke and axle did not move as it should not, but the axle shaft still turned freely as if it where not engaging. Does that make any sense or am i just missing something?

OK so if you don't have the axles bolted in then when you turn one with the driveshaft attached, the other axle will turn in the opposite direction. Since you don't have the axles bolted to the hub, nothing will stop the other axle from turning.

O.k., i thought maybe i just wasn't thinking about it right.

You're dealing with the differential action, this vidio,(Around the corner)
will explain what you are observing:

DG

Wow, thanks Denny, I've never been exactly sure just how the differential worked. That is a really good video to help explain it.

And now you know!

DG