38/44 diffs Q

[Straydog954]

Hi I was wondering if you can swap 38k rears into 44k housings as long as the axle shaft spline count is the same? Are they the same or are the 44’s built heavier?

[880joe]

I was always told they were the same

[mechohaulic]

follow up later with the correct results be greatly appreciated. the housings may be the same : axle spline possibly ok . my question based on failing ole man memory is the axle length.  out in left field on this BUT  38's have a solid axle while 44's have the floating axle as with the 55's ???? 

[Joey Mack]

What year are these axles

[fjh]

12 hours ago, mechohaulic said:

follow up later with the correct results be greatly appreciated. the housings may be the same : axle spline possibly ok . my question based on failing ole man memory is the axle length.  out in left field on this BUT  38's have a solid axle while 44's have the floating axle as with the 55's ???? 

yup valid question ! Axles are totally different and joey has a point to 44 change to a flanged axle at one point as well so year is important as well! 38 axles had a totally different flange at one point with different stud size AND pattern on earlier vins !!!

[Vladislav]

38 hubs have totally different flange. But axle spindles both of 38 and 44 have same sizes where hub bearings are fitted. So geometry of both axle housings seem identical. I mean length (width), hub bearings seat and also the spot where you mount the diff. Sure it's never wrong to double check sizes of the parts you use for a swap but just changing a diff from 38 axle housing to 44 doesn't seem bringing a trouble. Another point though the diff housing may have or not have studs where they're needed to be (if needed) or have different style of the torque rod attachment.

[Straydog954]

Both rears are crd 92 and 93 so they are the same regardless of being 38 or 44s I was told by Weller. These are 96 and 98 yr vintage. The axles are different length I assume because one rear has daytons and the other is hub pilot.  

[mechohaulic]

hopefully you have access to the donor truck if parts are needed. the 38's should have an axle with flanged end cap. 44's should have axle with splines on both ends with separate cap which attaches to the wheel , making the 44's tad longer and sticking out of wheel hub. easiest plan of attack have both axles =38 and 44 side by side.  axle in to the rear end side gears might/ should be same spline count.

[Joey Mack]

I dont recall the axles being different lengths..  

[Straydog954]

I would be keeping my housings and using my axle shafts and they are both 17 spline so everything should work out 

[Joey Mack]

Yes

[Vladislav]

As said above I guess.

To Mecho:

#44 axle shafts had separate cone at the hub end up to a certain year. Later axles became of a style with flange, like #38 were. With 6 mounting bolts thicker than 8 bolts in #38 flange.

 

[mechohaulic]

On 8/28/2024 at 3:25 PM, Vladislav said:

As said above I guess.

To Mecho:

#44 axle shafts had separate cone at the hub end up to a certain year. Later axles became of a style with flange, like #38 were. With 6 mounting bolts thicker than 8 bolts in #38 flange.

 

that's what threw this ole man off;; I didn't know there was a changeover later years going from separate axle cap duel end splined axle set up to one piece flanged style (cheaper to manufacture) axle on the 44 range. THANK YOU  for providing the info to expand knowledge.

[Vladislav]

11 hours ago, mechohaulic said:

that's what threw this ole man off;; I didn't know there was a changeover later years going from separate axle cap duel end splined axle set up to one piece flanged style (cheaper to manufacture) axle on the 44 range. THANK YOU  for providing the info to expand knowledge.

Yup, that fixed flange style showed up closer to the end of 80's as it seems to me.

I have a question to you though. My 1945 Mack model NR has those cone flanges arranged with double splined end axle shafts and elephant ears bogie to frame brackets what being seemed as #44000 setup. The matter is those "mushroom" flanges have oil seals installed in them. So gear oil from the banjo can't go into hub bearings and the latters are spinning in grease. At the same time I have a 1984 MH-model with similar looking axle flanges but those bearings utilize gear oil from the axle. Were both of the styles existed as different options or was there a swap from grease in the hub bearings to oil?  

[Joey Mack]

Interesting, Vlad..  I'm curious too..  I did wheel end work on a B-61,  and was able to find a good rear most axle seal, and removed the seal in the middle of the hub. This was on a working dump truck, that runs 4-6 days a week by one driver, ''the owner''... no leaks or other issues. 

[mechohaulic]

in earlier set ups, the outer bearing was oil fed while inner bearing was grease packed. with proper seal (oil capable) being installed in wheel and elimination of the middle (intermediate )seal both bearings became oil fed.

[mechohaulic]

9 hours ago, Vladislav said:

Yup, that fixed flange style showed up closer to the end of 80's as it seems to me.

I have a question to you though. My 1945 Mack model NR has those cone flanges arranged with double splined end axle shafts and elephant ears bogie to frame brackets what being seemed as #44000 setup. The matter is those "mushroom" flanges have oil seals installed in them. So gear oil from the banjo can't go into hub bearings and the latters are spinning in grease. At the same time I have a 1984 MH-model with similar looking axle flanges but those bearings utilize gear oil from the axle. Were both of the styles existed as different options or was there a swap from grease in the hub bearings to oil?  

now if your set up had/has the seal in the axle cap it self then both inner and outer bearings were/are grease packed. there is a set up with the seal inside having outer bearing oil with inner grease. changed a few in the day to oil on both. then it was stemco seals with the axle spindle wear ring.

[Geoff Weeks]

47 minutes ago, mechohaulic said:

in earlier set ups, the outer bearing was oil fed while inner bearing was grease packed. with proper seal (oil capable) being installed in wheel and elimination of the middle (intermediate )seal both bearings became oil fed.

Do you have a pictorial diagram of that? I've worked on plenty of greased wheel bearing/full floating axles, but never seen one with a seal between the inner and outer wheel bearing? I trying to imagine how that would work in practice, and I can't see why it would be done?  Either seal at the axle tube and grease the bearings, or let the oil spill and seal at the spindle.

 I've seen a few different ways used to keep oil off the bearings, but never one oil and one greased. 

[mechohaulic]

17 minutes ago, Geoff Weeks said:

Do you have a pictorial diagram of that? I've worked on plenty of greased wheel bearing/full floating axles, but never seen one with a seal between the inner and outer wheel bearing? I trying to imagine how that would work in practice, and I can't see why it would be done?  Either seal at the axle tube and grease the bearings, or let the oil spill and seal at the spindle.

 I've seen a few different ways used to keep oil off the bearings, but never one oil and one greased. 

a picture I do not have, sitting here brain cell working to remember exact set up. could almost say one set up was in the '65 #1 R model. which was the reason I started working there, some one did a rear brake job on it and did it wrong.  bearings seized to housing tube to point rear housing had to be changed. 

[Geoff Weeks]

I can see it as possible if the seal was installed behind the outer race of the outer bearing and sealed on the spindle, but would make the hub hard to install without damaging the seal. The question is why? If going to all that trouble, than why  not have both run in oil?  

 I'm curious because I have never run across it.  

Greased bearing have some advantages, and some drawbacks, but you have to seal the oil in somewhere, and doing either before or after the bearing both have good reason for that method, have one oil and one grease leave you with the disadvantages of both.

[Vladislav]

Definitely an interesting matter got digged out. I also haven't had idea on possible installation of the seal between the bearings. Looking by an engeneering (design) point of view I'm with Geoff - "not meat and not fish" as we would say where I am. So possibly some technological reason or reason of some other kind was involved.

[fjh]

25 minutes ago, Vladislav said:

Definitely an interesting matter got digged out. I also haven't had idea on possible installation of the seal between the bearings. Looking by an engeneering (design) point of view I'm with Geoff - "not meat and not fish" as we would say where I am. So possibly some technological reason or reason of some other kind was involved.

Old idealism over new in my opinion! Old habits die hard in the minds of some people! Engineers are not immune to this! That said if you don’t try stuff you don’t move forward! Sometimes it’s up to us in the field to do what they are afraid to do. I personally have done it! I’ve seen both setups both work ! Is the extra work necessary? If you got something that works why change!?

 

[Geoff Weeks]

32 minutes ago, fjh said:

Old idealism over new in my opinion! Old habits die hard in the minds of some people! Engineers are not immune to this! That said if you don’t try stuff you don’t move forward! Sometimes it’s up to us in the field to do what they are afraid to do. I personally have done it! I’ve seen both setups both work ! Is the extra work necessary? If you got something that works why change!?

 

I agree, when we are talking about grease vs oil in the wheel bearings, but that kinda falls  apart when you make a set up that has one run in oil and the other in grease.

 Both greased and oiled bearings have proved successful. It took making a seal between the hub and spindle that could hold back oil in that environment. Once we had that, most elected for oil, just simpler and there is no doubt when you have a leak. 

 That still leaves the question why you would make the 1/2 step of one in grease and one in oil?

 Trailers and non driven hubs are going back to grease, (abet different grease than the 60's) and in some applications old grease is still preferred. 

 Driven axles have a problem others don't, you have to hold the oil back somewhere, in  the axle tube, at the outer end of the shaft or at the hub/spindle joint. It makes the choice less clear cut.

 When old wheel seals were felt or leather, there was little choice. Stemco came out with the 1st hub seal at the spindle (was still leather at 1st IIRC), but the wear surface was changed each time the hub was off. Rubber was used at the axle flange end as it was away from the brake heat, to keep the oil out of the bearing area.

 Some of the old felt/ leather seals can be replaced by modern unitized seals, but not all can, depends on how the hub end is constructed.

[Mark T]

Don't forget, back when seals were like that lots of stuff we take for granted weren't around then. Some things could be retroed and some couldn't.

[Geoff Weeks]

At this point it is unlikely that we will know the reason for what Mecho described, as I have said, I have never seen a hub where the outboard bearing ran in oil and the inboard in grease. 

 I have seen several ways they hold the oil back, at differing places on the hub, but never one where one of the two wheel bearing are in oil and the other in grease. I am intrigued! 

 Jojo and I both have trucks that had felt wheel seals, with greased bearings. On the drive axle you can install a modern unitized seal in place of the felt, but on the steer axle you would to machine parts to allow for a rubber lip seal to be used. The felt seal is pinned to the knuckle with felt compressed between two washers that are squeezed by the rear bearing, If you remove the washers and felt you need to make a "dummy" wear surface to fit over the pin and hold the bearing is correct alignment, then a seal could be found to be pressed into the hub and ride on the new surface. The original had the seal stationary and the felt road in the inside of the hub bore.

 The replacement front seal would have to be very narrow as was the original felt. As long as all the original parts are still on the hub, you can cut new felt and throw it back together.

Edited September 2 by Geoff Weeks