79 GMC K25 hub help

[Nontwisty396]

Question about removing hub/rotor assembly on a 1979 GMC K25 with full time GM10 bolt front diff.
Someone (long before I got this truck) installed DualMatic locking hubs on the beast.
My problem is that I need to replace the ball joints, but can't seem to find any info on how to remove the hub/rotor assembly.
I got the locking hub off, and the snapring off the end of the axle, and the lock-ring from the inside lip of the housing.
That's as far as I can get. Someone in the past has obviously had trouble removing the slide gear(?) as it's got a couple of pieces missing from the outer ring.
Can anyone tell me if I'm missing a spring clip or something? Can't seem to find any diagrams that show the assembly that I have.
The closest I can find is a Selectro diagram, but while the hub handle matches the rest of the parts are different.
The hub handle leaves a gap that could allow dirt/sand/water into the assembly, so I wonder exactly what kind of a bastardized setup I bought?
Thanks to anyone who can help!

[Nontwisty396]

If I were more tech saavy I would post pics of the assembly...
The axle gear turns separately from the slide gear, and looks like once the spring clip was removed from the axle, the axle gear should come out, but it moves in and out with the slide gear, and will not come out separately. I've looked for hidden clips, pins, everything I could think of. No luck.
Both sides are the same issue, so it's not a burr on the axle or something simple like that.
I know it's probably something simple I'm missing, and if I had hair I'd be pulling it out right now.

Any ideas?

[Nontwisty396]

If I have this right you should be able to see what I'm working on...

[nonstop]

Never worked on the dual matics, but just making sure, you got the snap ring out of the wheel hub that retains the aluminum hub? Can't tell from the picture on my phone.....

[Nontwisty396]

Yeah, my pic doesn't show it very well. The snap large snap ring is next to the hub handle in the pic next to the hub handle. The axle snap ring is sitting inside it. The other ring in the pic is the rubber o-ring that is suppose to seal the aluminum hub and the wheel hub.

The axle will pull back flush with the end of the inner gear, and the gear slides easily back and forth on the axle splines, so there's not a burr or clip or anything there.

The aluminum hub slides in and out in the wheel hub about 1/4" then stops. It feels like there's a clip or snap ring or something behind that aluminum hub, but believe me I've looked without success.

Thanks for any ideas or help!

[Nontwisty396]

Well I've talked to a lot of different people, from 4x4 forums to offroad "experts", to old-school mechanics, and nobody so far has come up with the answer.
Everyone gets stumped when I tell them the inner gear slides freely until just before clearing the outer hub, then stops. Same on both sides, so kinda eliminates the rusty parts idea...
The one suggestion I haven't tried yet is to simply use a slide hammer gear puller and 'pop' the thing apart. The only problem there is I'm afraid it'll destroy the parts. And I don't have spares...
If I can't find a solution soon that may be my plan.
That said, if it does break the part, I need to have a backup plan with backup parts. May be a good opportunity to do an upgrade anyway.

Any ideas, before I bust out the puller?

[cadillac_al]

It looks to me like you are ready to take the spindle nut off. It takes a special socket that is sold at the parts stores.

[bluek5]

I think that it must have a burr somewhere that is preventing them from sliding out. I have a single Dualamatic hub if you end up damaging yours. If you have both snap rings removed, I would use a slide hammer to get them out.

[Nontwisty396]

Thanks guys. Yep, both snaprings are out and the outer gear slides freely til it just stops. Same spot on both sides. And when it stops it doesn't get tight, I can rock it, it just won't come past that point. It acts like the inner gear that slides on the axle is somehow connected to the outer gear that slides into the hub. As you can see in the pictures someone either damaged the outer gear offroading or by trying to get the thing apart before I got it. I've worked on a lot of these in the past that had a different set of gearing inside, where once you removed the snaprings all slid out to expose the bearing jam nuts.

[Nontwisty396]

BlueK5, I see your dualmatic hub is on a half-ton, and mine's a heavy 3/4 ton. I wonder if the innerds will work.
I see the same gap around the hub handle and the rotor hub on yours that mine has. Wonder if that's just the design, or if they really weren't meant for these assemblies? Seems like a lot of grit can get in, even though there's the small o-ring.

[bluek5]

I think from mid 77 up the 1/2 and 3/4 tons used the same locking hubs. Mine is out of a 72 Blazer. Yeah, if I remember correctly there is an o-ring on the outer handle that seals inside of the inner edge of the hub.

[Nontwisty396]

I'll bite the bullet and try the slide hammer.
I need to get in there to replace the ball joints, and haven't obviously checked the beariings since I got the truck over a year ago...not like me, usually a little ocd...lol
If I DO break anything I'll get in touch to see what you might want for your hub.
72 Blazer? Nice. I'm slowly restoring a plain old 72 C20. Love the body style!
Thanks guys! I'll let you know how it goes.

[74CustomK20]

At least if you break one side you'll know for the other side.

[Nontwisty396]

That is very true. And if I DO break one side at least the truck should be driveable, just won't have 4x4 option.

[hatzie]

These Selectro, Dualmatic, Sears, etc hubs were made by Mile Marker for more than a few axles in the 1960's & 1970's.
You may be able to find documentation on their web page.

[Nontwisty396]

Thanks guys!
Looks like I have a 77-83 K30 front axle. That explains why none of the other diagrams matched up. Now to see if I can pull the shaft drive gear out to get to the shaft drive spacer, and then get to the bearing nuts and bearings.
Tomorrow...

[83GMCK2500]

Originally Posted by Nontwisty396

Thanks guys!
Looks like I have a 77-83 K30 front axle. That explains why none of the other diagrams matched up. Now to see if I can pull the shaft drive gear out to get to the shaft drive spacer, and then get to the bearing nuts and bearings.
Tomorrow...

K30 front axle is a Dana 60, which has king pins as opposed to the ball joints that are clearly visible on your axle. There were two different Dana 44s, a large hub and a small hub, that could be why you're having problems. For Dana axle ID check the attached picture.

[hatzie]

I looked at the pictures closer. GM started to use 10 bolt axles in the late 70's. Those look similar to the 10 bolt cast iron hubs. Are you sure it's a DANA 44?

In any case there should be a spring steel wire ring that holds the outer alloy splined section of the Selectro Dualmatic hub-lock to the cast iron hub. It's probably buried in mud, grease, and crud. You'll have to dig for the ends and dig it out with a pick or similar weapon. Once that ring is out of the way you can remove the alloy piece with the chunks missing.

If you can't get a replacement for that beat up piece I'd consider getting new hub-locks.

[Nontwisty396]

I literally just pulled the truck into my shop so I can see if I can identify exactly what unit I am dealing with...
I've cleaned the inside of the assemblies out with solvent so I could try to locate a hidden clip or spring.
The inner gear moves 'in and out' separate from the alloy piece just enough to come past the end of the axle shaft, then stops. The alloy piece moves freely in and out until just past the lip of the housing, then stops. Same place for both parts on both sides. That's what makes me think I'm overlooking a clip or spring somewhere.
I sure appreciate all you guys helping me out here. I've had dozens of hubs and front ends apart, but this one has me stumped.
In the next half hour or so I'll try to pop the inner gear out again.

[hatzie]

There should be a ring of spring wire in a groove just inside the lip on the cast iron hub.
You should be able to pick it out with a screwdriver or seal pick.

[Nontwisty396]

Got the flat spring out of just inside of the cast iron hub. Got the circlip of the end of the axle shaft.
Still, even with visegrips on the alloy part to pry on, no go. It acts like there's another clip or spring deeper in the assembly that I haven't found yet. Everything moves freely, so no rust gunk or burrs.

[Nontwisty396]

If I can get modern technology to cooperate I'll show a couple of pics.
Looks like from some diagrams and pics I found online that I have a Corporate 10 bolt 8-1/2" front diff.

[Nontwisty396]

Sorry pics aren't great. IF they come thru...
The diff pic shows the ears at the bottom that apparently identify it as a Corporate diff.
The pic of the hub has arrows pointing at where I've removed clips.
I have used a small file to make sure no burrs on the end of the shaft preventing the inner drive gear from coming out.

[hatzie]

That's a GM 10 bolt front axle. The DANA doesn't have those ears of cast under the bottom corners of the cover. The 10 bolt diff cover is smoother than the DANA covers too.

They are very similar axles but not exactly the same.

Download the 1981 service manual and go to page 315 for a cutaway view of the innards.

[Nontwisty396]

If the diagram you refer to is correct, I must not yet have found the snap ring #24?
Looking at the diagrams for 77-83 K30 Corporate front axle the parts look very similar to mine. The part #75 looks like the snapring at the end of the axle that would hold the inner gear #74? on the axle shaft. I'm assuming if that's correct the gear should slide off the axle shaft once the snapring is removed to allow access to part #75 spring clip that may hold #73, drive gear spacer? Not sure... Gonna try again to see if can remove the inner gear. When I rock the outer cage alloy part the inner gear moves with it, as though they are attached...