Eaton HO72/HO52 vs. 14 Bolt FF

[63GMCKid]

I'd like to start another thread dedicated to Eaton tech exclusively, mainly due to the fact that even though the Eaton the 14bff share some similar parts, they are two totally different animals, and there isn't a hell of alot to compare. Not to mention the Eaton is way cooler than the 14bff.

To break it down, the only parts interchange between an Eaton and a 14bff would be.....

-Lunchbox lockers for the 14bff will fit in the Eaton.

-The Eaton and 14bff carrier, while different from each other, will accept spider and side gears (and lunchbox style lockers) from either model.

-Disc brake brackets for an SRW 14bff will fit an SRW Eaton IF the Eaton has stud retained drums. Yes folks, some of the HO52's/72's had slide on drums (SRW models only), in my experience it has typically been the older ones. If your Eaton HO52/72 has slide on brake drums, the disc brake conversion brackets from a 14bff WILL NOT WORK! They will bolt up, but the Eatons with slide on drums have a different hub and slightly shorter spindle than the Eatons with stud retained drums. A hub with stud retained drums will fit on a housing that originally had slide on drums, but this WILL NOT solve the problem, as the spindle on the slide on drum Eatons is physically shorter and puts the entire hub/disc assembly too close to the caliper bracket. Believe me on this one, I found out the hard way.

In simple terms, if you want disc brakes on your Eaton HO52/72, you can NOT use an Eaton housing/hubs that originally had slide on drums, you MUST use a housing/hubs with stud retained drums.

For the rest of the disc brake conversion, the game of finding the right studs to use is tricky, as Eatons use smaller 1/2'' studs compared to the 14bff's 9/16'' studs. I drilled out my hubs to use larger 9/16''-18 wheel studs, then used the recommended Dorman stud that is used for a 14bff disc brake conversion. The discs/calipers used are the same, standard chevy 3/4 ton D44/10bolt front rotors and calipers.

And for clarification, stud retained drums means the brake drum is held to the back side of the hub with the wheel studs being pressed through the drum/hub, meaning the only way to service the drum brakes is by removing the axle shaft and hub/drum assembly. Slide on drums means the drum slides onto the front of the hub over the wheel studs before the wheel, and does not require removing the axle shaft or hub to service the drum brakes.

-Axle shafts can be interchanged between the Eaton and 14bff, HOWEVER, the Eaton HO52's/72's have 17 spline shafts/side gears, the 14bff has 30 spline shafts/side gears, but side gears can be swapped between the two. Eatons with slide on drums have shafts that are approximately 1/4'' to 1/2'' shorter per side (per shaft) than Eatons with stud retained drums, but the spline count remains the same.


To my knowledge, this is where the similarities end. Parts interchange is minimal as noted above. I am not sure on all of the bearings, but I know for fact (as per GM Archives) that the Eaton wheel/hub bearings are different than 14bff wheel/hub bearings. The main pinion bearings are obviously very different between the Eaton and 14bff, and there are two different types of pinion bearing used in the Eaton, a ball bearing, and a taper roller bearing, there is no order to when what bearing was used, in my experience they are all mix matched together through their 1947-72 production run. As for the 3rd pinion bearing, that's your typical needle/roller bearing, unsure if they use the same one for the 14bff and Eaton. I am also unsure about any carrier bearing interchange, but I know the Eaton originally used Hyatt barrel type bearings for the carrier. Aftermarket replacements are typically Timken taper roller bearings.


And to clear up any confusion about available ratios, there are 3 common ratios for the Eaton and 1 mythical ratio.

The common factory ratios were:
4.10 (41 tooth ring,10 tooth pinion) (According to the GM Archives, later ones were 4.11, with a 37 tooth ring gear and 9 tooth pinion.)
4.57 (32 tooth ring, 7 tooth pinion)
5.14 (36 tooth ring, 7 tooth pinion)

Then the mythical ratio that no one has yet to find, is a 5.83, which would be a 35 tooth ring gear and a 6 tooth pinion. According to the GM Archives, it was only available in 1963 and only an available option for P30 series vans. It may or may not have actually existed, but the GM Archives says it did. Considering the low performance of engines at the time, and lack of an overdrive transmission, I'm sure this was a very undesirable option, and if any were ever made, I'm sure not many ever ordered in a 1963 P30 van, the only vehicle that it could be had with. This is somewhat of the holy grail of Eaton gear sets though, and I would bet it could fetch a fairly large sum of dough to the right person.


For tons of good info on the Eaton, you have to look past some of the typical BS associated with Pirate4x4, but if you can get around that, there is a wealth of knowledge about Eatons in this thread, page 20+ and beyond/current is where there is A LOT of tech. http://www.pirate4x4.com/forum/chevy...aton-h072.html

[jbclassix]

That's the Eaton guy there.

As for bearings, None are interchangeable. I tried. Only bearing I have not checked on yet is the pinion support bearing.

Stay tuned. If I can find someone to machine my 14 Bolt hubs for cheap (free) I will show you what I have to do to run the 14 Bolt parts on my Eaton.

Edit: don't forget about the mythical 3.92 ratio discontinued aftermarket offering.

[63GMCKid]

Originally Posted by jbclassix

That's the Eaton guy there.

As for bearings, None are interchangeable. I tried. Only bearing I have not checked on yet is the pinion support bearing.

Stay tuned. If I can find someone to machine my 14 Bolt hubs for cheap (free) I will show you what I have to do to run the 14 Bolt parts on my Eaton.

Edit: don't forget about the mythical 3.92 ratio discontinued aftermarket offering.

Well if the tech isn't enough proof for some, does owning 6 Eaton HO52's/72's (2 C&C's, 1 Front Eaton60, and 3 SRW's) prove I'm an Eaton guy for sure?

I've heard various rumors about the aftermarket gearsets available for these. I know for fact that it was Randy's Ring & Pinion that had a limited production run of like 10 of those gear sets made, and I've seen mention of several different numbers. Most times that those aftermarket sets were brought up in the thread on Pirate, they were referred to as being a 3.73 gear set. I've heard 3.90 and 3.92 thrown around on here. I have yet to see a picture of these aftermarket gears, likely because of the fact that they were made in such a limited number.

I'm curious to know what the R&P tooth count was for those gears too. According to Tim Cooper, the guy on Pirate4x4 that machined a 14bff ARB air locker to fit in an Eaton, (he seems to be an Eaton guru, but only posted a few pictures to make us all drool over the possibility of an ARB for the Eaton and some tid bits of tech), the 4.57 gear set is the strongest because of the 7/32 tooth count, the ring gear is thicker than any of the other gear sets and it has larger/coarser teeth than the other ratios. There has been 1 person on Pirate in the several year/30+ page history of the Eaton thread over there that has managed to grenade two 5.13 ring/pinion sets in a pulling truck, and the shredded gears were quite spectacular (and somewhat saddening) to see. Compared to the amount of shredded 14b gears that are seen over there, I'd say that's pretty impressive, but I doubt anyone with those low ratio aftermarket gears from Randy's would be abusing them quite like us offroad guys do.


And I'm interested in seeing some 14b hubs put on an Eaton, I'd love to make the rear HO72 in my GMC into a 67'' wms width axle without the use of spacers or extending the housing. 14b hubs should make it that wide I would think. If I were more skilled with a lathe (I have free access to one at work), I'd try to machine a set myself, but I'd be afraid of ruining the hubs.

EDIT: After looking at your pictures on page 1, I think there would be some issues with disc brakes and 14b hubs on an Eaton, because the drum/rotor mounting surface on the back of a 14b hub is moved further out on the hub than it is on the Eaton hub. Why would this be a problem? Simple, the same reason why all of the same disc brake conversion stuff works on an Eaton. The "backing plate flange to machined drum/rotor mount surface on the hub" distance is the same for the 14b and the Eaton. Since that surface is further inboard on the Eaton, so is the backing plate flange. If you move that drum/rotor mount surface further outboard, which is what you would be doing by putting a 14b hub on an Eaton, then your drum/rotor will be too far away from the backing plate flange, probably by about 1'', since that's the width difference per side between an Eaton and 14bff. This probably could be solved with weld on caliper brackets or a simple spacer, but just something to keep in mind there. Bearing spacing is the other thing I'd be concerned about when trying to fit 14b hubs on an Eaton housing. I can check for you tonight if the bearing spacing is the same for the 14b and Eaton hub, since I have a 14b housing with no hubs and a couple Eaton spindles I cut off for my Eaton 60, I can compare the two and get some measurements.

[roadmaster301]

What exactly is needed for the HO72 disk brake swap. Do you just need the caliper brackets for a 14 bolt, disks, and caliper. Or do you need 14 bolt hubs too and possibly more parts?
Posted via Mobile Device

[jbclassix]

Originally Posted by roadmaster301

What exactly is needed for the HO72 disk brake swap. Do you just need the caliper brackets for a 14 bolt, disks, and caliper. Or do you need 14 bolt hubs too and possibly more parts?
Posted via Mobile Device

You do not need the 14 bolt hubs.

Use the recommended calipers and discs for whatever conversion kit you order, as well as the wheel studs.

[496bb]

Thanks for all the good info. I have discovered that my 69 C20 has and Eaton rear. I will post a few pics this weekend. In using an online gear ratio calculator I had determined that I had 4.88, but apparently my Autogage tach may be a bit off or 40+ speedo - as they must be 4.56/57 gears.

I have an AX15 trans that I wanted to install, but thinking I still may need to try and find a 4.10 center section to get my rpm's to a comfortable highway cruising speed.

Dumb question, what's the easiest way for me to tell if I have the "no-spin" locker? And what should the width be on this axkle from mounting flange to mounting flange?

I like different, which is why I want to keep the Eaton, and rebuild the 307 - and keep this truck an 8-lug working truck. I would like to change out the coil springs - as this truck (when unloaded) has an extremely harsh jolt when you hit a bump. Anybody know what the factory spring rate would be for a coil sprung Eaton C20 LWB (base truck), so I can compare and get a slightly more forgiving spring? I also have aftermarket airbags installed on the axle so if I decided to load the bed down, I have extra help without the harshness day-to-day of these stiff coils.

But if I did find a 12 bolt that would direct swap in with no real mods and a better gear, I might consider.... So far only found a Dana 60 out of a ford and the guy says it is 74" wide, way to wide I think based on what I see so far. Of course, there's always the thought of doing a dually axle

[bignbad]

I am curious they sell 14bolt ff spindles can they be put on the Eaton ho52 and use the 14bolt ff hubs and put a disc brakes on them

[jbclassix]

Originally Posted by 496bb

Thanks for all the good info. I have discovered that my 69 C20 has and Eaton rear. I will post a few pics this weekend. In using an online gear ratio calculator I had determined that I had 4.88, but apparently my Autogage tach may be a bit off or 40+ speedo - as they must be 4.56/57 gears.

I have an AX15 trans that I wanted to install, but thinking I still may need to try and find a 4.10 center section to get my rpm's to a comfortable highway cruising speed.

Dumb question, what's the easiest way for me to tell if I have the "no-spin" locker? And what should the width be on this axkle from mounting flange to mounting flange?

Jack up both wheels with the transmission in park, and the front wheels blocked. Rotate one wheel. If the oposite wheel spins the oposite direction it is an open differential.

Originally Posted by 496bb

I like different, which is why I want to keep the Eaton, and rebuild the 307 - and keep this truck an 8-lug working truck. I would like to change out the coil springs - as this truck (when unloaded) has an extremely harsh jolt when you hit a bump. Anybody know what the factory spring rate would be for a coil sprung Eaton C20 LWB (base truck), so I can compare and get a slightly more forgiving spring? I also have aftermarket airbags installed on the axle so if I decided to load the bed down, I have extra help without the harshness day-to-day of these stiff coils.

1/2 ton coils are a direct bolt in and readily available. I hope this helps!

Originally Posted by bignbad

I am curious they sell 14bolt ff spindles can they be put on the Eaton ho52 and use the 14bolt ff hubs and put a disc brakes on them

the 14 bolt disc brake conversion kits are a direct bolt on to the HO52/HO72. you do not need to use the 14 bolt hubs.

[496bb]

Originally Posted by bignbad

I am curious they sell 14bolt ff spindles can they be put on the Eaton ho52 and use the 14bolt ff hubs and put a disc brakes on them

As in the kit from Blackbird, or something different?

[bignbad]

forget about the disc brake kit.. in general put a set of 14bot ff spindles on the eaton and run the 14bolt hubs.. its cheaper to get bearings for the 14bolt hubs then the eaton hubs. then add the disc brake kit theres at least 4 place that make the brackets for the disc brakes

[jbclassix]

Originally Posted by bignbad

forget about the disc brake kit.. in general put a set of 14bot ff spindles on the eaton and run the 14bolt hubs.. its cheaper to get bearings for the 14bolt hubs then the eaton hubs. then add the disc brake kit theres at least 4 place that make the brackets for the disc brakes

I get what you are saying now. Cut off the Eaton Spindles and run 14 Bolt stuff. By all means, if you have the capability, DO IT!!! One of the guys on a particular 4x4 forum machined the spindle to accept the inner bearing cone, but I don't know about the thickness of that part of the spindle.

[496bb]

[IMG][/IMG]



So I have the taper bearing, correct?

[63GMCKid]

Originally Posted by bignbad

forget about the disc brake kit.. in general put a set of 14bot ff spindles on the eaton and run the 14bolt hubs.. its cheaper to get bearings for the 14bolt hubs then the eaton hubs. then add the disc brake kit theres at least 4 place that make the brackets for the disc brakes

Eaton wheel bearings don't cost that much more to make it worth it to swap spindles. And in order to do it properly, one needs the proper tools, as in a setup bar and pucks to put in place of the carrier bearings, a large 220v welder (MIG or TIG), a lathe, grinder, etc. So on that note, run the EXACT SAME KITS used for the 14b disc brake conversions, using the same parts for those conversions, on the Eaton hub, it all fits just the same unless it's an early Eaton. No reason to reinvent the wheel here, there is a reason why us Eaton guys don't bother to swapping spindles.

[63GMCKid]

Originally Posted by 496bb

[IMG][/IMG]



So I have the taper bearing, correct?

Yes that has the taper roller pinion bearing. Note the oil return port at the 5 o'clock position on the pinion bearing/seal retainer flange, and the extra casting hump above the pinion for the oiling port, next to that central stiffening rib on the 3rd.

[496bb]

Took a wheel off today and I am pretty sure I do not have slide on drums. Also appears to be an open diff, confirmed that and my gearing by about 2.25 turns of the driveshaft per wheel revolution.
So, can somebody give me a little more direction on who/where to get the disc kits from?

In the meantime, is there a way to adjust the ebrake without pulling the drum?

[vectorit]

Your adjustment window is right there.

[496bb]

That's what I thought, and thought there was like a "star" shaped adjustment gear but as I spun the hub around and tried to use a light looking throught there to find it I didn't see anything. Pardon my ignorance here. Where (like clock position) should the window be to see, and what's the proper procedure for adjusting the ebrake a little tigher?

[SS Tim]

The window is for adjusting the shoe to drum clearance. If that is correct then you need to adjust the park brake cable at the equalizer.

Why do you feel you need rear disc brakes and why would you depend on a car rated caliper park brake for a 3/4 ton truck?

Service Manual Downloads
http://67-72chevytrucks.com/vboard/s...d.php?t=570059

[vectorit]

Put the window at the 6:00 position.
Seeing the star wheel may be a little tough, since it is probably darkened up with brake dust.

The E brake adjustment is under the truck below the driver seat position.

[496bb]

Ok, thanks for the insight guys - that pic helps greatly.

Tim, I don't necessarily think I need the disc brakes out back- but from what I am reading it will be expensive and hard to find parts to rebuild the brakes should this eaton need drums and other brake parts down the line. I will be tearing the truck down soon and rebuilding from the ground up. If the drum brakes are serviceable, I will just run them awhile longer. I have the PB/PS from a 72, and will be finding some 73-87 spindles to upgrade the front to discs(although I hear the PB upgrade even with drums is an improvement).

This truck will not be used for seriously heavy work, although looking at the steel plate the PO welded in to the frame for the 5th wheel ball seems to indicate that it has been in the past. PO told me they used it to haul horse trailers.

I have adjusted the ebrakes as you suggested, and they are better. When I tear down and rebuild the truck I will be using another ebrake pedal assembly that is hopefully in better working order than mine. I just thought there was also an adjustment at the drum, I guess that's for the main brake shoes.

Thanks again for the help guys. Now if I could find a 4.10 third...

[bignbad]

Originally Posted by 63GMCKid
Eaton wheel bearings don't cost that much more to make it worth it to swap  spindles. And in order to do it properly, one needs the proper tools, as in a setup bar and pucks to put in place of the carrier bearings, a large 220v welder (MIG or TIG), a lathe, grinder, etc. So on that note, run the EXACT SAME KITS used for the 14b disc brake conversions, using the same parts for thosreinvent the wheel here, there is a reason why us Eaton guys don't bother to swapping spindles.e conversions, on the Eaton hub, it all fits just the same unless it's an early Eaton. No reason to

i checked on wheel bearings a t a napa store and its going to cost around 300 for both sides when i just replaced wheel bears and seal on a 14bolt for around 100 so i think ill be saving 200 on wheel bearings what do you think?And my spindles are pitted here and there on the eaton so i think ill replace my spindles with 14bolt ff's i can by them for 100 and there a fab shop that will put them on for me for 40 an hour or option 2 is i know a guy thats a welder for the gov. he'll do it for a case of beer plus i help out and lean. Beside i have a 110,220, and a 480 welder pluse plasma cutters and so on. i think i could do it my self but i want a cert. welder doing it... thank you for your support

[PortalAxls]

Well I heard back from Right Gear & Axle. Their kit works with the non servicible drums. Once I find a donor axle for the brake parts I will order the adapter and let you guys know how it works out.
Posted via Mobile Device
Posted via Mobile Device
Posted via Mobile Device

[haminator]

Wow, this thread is great. I think I know the answer but will a 14 bolt pinion support mate to the Eaton? If so then would a 14 bolt ring and pinion work in a Eaton? That huge Eaton pinion bearing most likely screws up that whole idea but i thought I'd ask. I want to keep my Eatons in all my trucks but 4:10s are really just too low for highway use these days. I've got 4:56"s and 5:14's too. Also the adjuster on the side, is that for pinion side load? My 63 unit doesn't have that.

[jbclassix]

Originally Posted by haminator

Wow, this thread is great. I think I know the answer but will a 14 bolt pinion support mate to the Eaton? If so then would a 14 bolt ring and pinion work in a Eaton? That huge Eaton pinion bearing most likely screws up that whole idea but i thought I'd ask. I want to keep my Eatons in all my trucks but 4:10s are really just too low for highway use these days. I've got 4:56"s and 5:14's too. Also the adjuster on the side, is that for pinion side load? My 63 unit doesn't have that.

The adjuster on the side is to prevent ring gear deflection. It is a common component on Heavy Line trucks like 18 wheelers, and such.

Interesting that you should ask that about the 14 bolt R&P. As for the 14B pinion support, no, it will not fit. The pinion support has a larger diameter than the eaton pinion bearing set. the 14 bolt pinion is longer, and the pinion pilot is different. One KEY measurement that I don't have yet is pinion height for the Eaton. the 14 bolt is -1.50". I have several axles torn apart at home. I will take pictures of the differences when I get home.

[jbclassix]

Here are some side by sides of a 14 bolt pinion support and the Eaton Bearing retainer.





Eaton pinion bearing and 14 bolt pinion support