Leaking Rear Hub on DP

[oldmattb]

My hub started leaking recently. This will be my first experience with this.

First, I am assuming that this is likely just a leaking cover plate, and not a symptom of something serious. I see no cracks nor damage, and there appeared to be a piece of thin gasket material sticking out from between the plate and wheel. Second, I assume the lube is the same that is in the differential, since there are no caps or fittings to install lube at the wheel.

Third, I am thinking the repair would be to drain the diff, remove the plate, clean up the surfaces, install gasket and reinstall.

Am I on track? Is it necessary to drain the diff? Would blocks of a safe height under the wheels on one side keep the fluid at bay until I could to the repair? Should I use a factory gasket, or will RTV do the job?

Or am I way off?

Matt B

[oldmattb]

It did not have the keepers. Twelve bolts twelve flat washers and the axle. The bolts were the kind with some locking action - bent slightly at the tops to create resistance on the threads. As of a few hours ago, no ooze, but it will take a good drive to really test it.

I found wildly divergent torque specifications for Eaton axles, and it seems to be dependent on the nut size. I found no spec for 3/4 inch bolts, so I shot for a figure between those listed, and settled on 135 ft/lb.

Matt B

[j-d]

Good on YOU! Did it have those "keepers?" Sounds like yours didn't.

Please let us know if it's stopped oozing.

[oldmattb]

Capstone-

I drove the coach up on some 2X6 pieces that I use for support when I work under the coach. This provided about 3-3.5 inches of lift on the offending side. I removed the bolts and washers. There is not much to grab the axle with, so I gave it a smack with a mallet, about what you would use to start a nail.

The axle moved out about i/8 inch, which allowed me to get a hook behind it. It slid out easily. It feels like it probably weighs 75 pounds.

The lube was still slowly flowing from the axle, so I built a little dam from paper towels to keep it backed up. I cleaned the sealing surfaces with acetone, and used differential RTV recommended by my local auto parts store.

The axle slid in 95 percent of the way with no interference. I remembered the orientation of the axle to the hub, turned it, gave it a wiggle and the splines mated.

I then pulled it out slightly and removed my paper towel dam. Washers and then bolts slightly tight for the RTV to set. I have not found torque specs for my particular axle, but similar ones were around 100 ft/lb.

This was an easy job, and I thank you guys for the information and encouragement. It took probably 1/2 hour, working slowly and carefully. It seems to me there are two tricks - stop the lube from running so the RTV can get a grip on the mating surfaces, and remember how to orient the axle so the holes match the studs before you make a mess of the uncured RTV.

Matt B

[j-d]

I hope so, and it's sure possible. There stands a big 22.5 tire with a 6" hub in the center. A diesel takes a thousand pounds torgue, gears it down, and twists that little 6" hub with enough force to accelerate 30,000 pounds to 80-mph. Just might work loose...

[oldmattb]

Thanks so much for the information, guys. I will research the proper torque specs, and tighten.

I think this may be a result of several miles of washboard dirt road last weekend. I never thought about hubs, I was expecting a TV in my lap!

Matt B

[VintageRacer]

If the back of the wheel and drum assembly is dry, I would absolutely torque the axle flange nuts up. Can't hurt, and will probably help!

Edit; I looked in my manual but couldn't find a spec for those nuts on my bus.

Brian

[pigman1]

Rvpapa wrote:
There are no other seals inside. If you could loosen those nuts with an 8" handle just tightening them up may fix your leak. Google "full floating axle" and you will find all kinds of info and pictures.
Art.

I agree. I've had axles like these leak on two different rigs, but in both cases all that was required was to re-torque the nuts holding it to the hub. If that doesn't help, the gasket behind the plate needs to be replaced. Easy to do, and the gasket is a very thin paper gasket. If you jack that wheel up as high as possible, (1" to 2") you won't have to drain the differential. You'll get a few drips out when you loosen the axle, but not a gush. Gaskets are available at any truck repair place.

[Rvpapa]

There are no other seals inside. If you could loosen those nuts with an 8" handle just tightening them up may fix your leak. Google "full floating axle" and you will find all kinds of info and pictures.
Art.

[oldmattb]

I may have been missing an important point that was hinted at, but not explicitly stated. Does the fact that there is lube leaking at that point indicate that an internal bearing seal, and not just the seal that mates the axle "cap" to the wheel, has failed? In other words the leak of lube at the outside plate of the axle is just a symptom of a problem further in the axle?

Matt B

[j-d]

I repaired buses for a church. Those axles were not as HD as the rear of your DP. The Brits don't call the rear "The Big End" for nothing

Those buses had the "full floating" rear axles (meaning the Axle Shaft is Drive Only, Rear Axle Weight completely isolated to Bearings) and the studs holding the flanges passed through tapered wedges like this

You can get the nuts and any washer off easily, but the axle itself may not give up easily at all without a puller and/or trick or two. You might/should be able to see the split of the wedge, called KEEPER, with a nut off. It'll look like an ordinary split lock washer stuck down in there.

Oh, a DP is the equivalent of a "Spec Truck" where the make/model of that axle is more significant than of the coach. Still, your coach builder or truck shop should be able to determine what you actually have under that Big End.

Rear Drum or Disc Brakes? The buses never leaked at the Flange! It was Inner Seals, and the interior of the hub (that you can't see when installed) had a groove to sling lost lube into a few holes back out to the outside. Purpose was to keep oil off the brake linings as long as possible.

I forget where the oil relief holes came out. The buses were rear drum. Pulling just that shiny simulator might get you closer to the source.

[Corkey05]

Oldmattb, ... both times my wheels were removed to avoid damage to the wheel openings when handling the axel. The outside hub and the axel are a single unit. Looking at your wheel you could probably pull the axel, clean it up and reinstall without jacks (no wheel removal). Cummins did mine both times and removed the tires/wheels to gain better access to the axle when removing it. Yes it's heavy.

[oldmattb]

I easily loosened one of the nuts with a socket and 8-inch handle. Maybe I should get a torque value and wrench the nuts down and see if that solves the problem?

Matt B

[oldmattb]

Tires have not been off recently.

No signs of oil on the backside, nor between the inner and outer wheels. It appears that the lube leaked from the outside axle plate and was driven by centrifugal force to the back side of the stainless trim cover.

I looked for a diagram or photo of how the axle comes apart, but could find none. So the 12 nuts come off, the axle just slides out and the hub remains attached to the axle? Does the tire and wheel have to be removed, or can this be done as it sits?

I am picturing removing the 12 nuts, pulling the axle out about 1/2 inch, letting some goo drain out, remove old gasket material and oil from mating surfaces, apply Permatex, tap axle back in, and install the nuts.

I value your sage advice, but I don't see where the jacks and stands come in.

Matt B

[Corkey05]

VintageRacer wrote:
Most times when someone has a leaking rear hub it's the inner oil seal. If you have a leak at the axle gasket, then all you need to do is take off all those nuts. slide the axle out, clean off the goop and old gasket, and put it back together. A factory gasket would be best but I would probably use "the right stuff" from permatex/loctite. You don't have to drain anything, or take anything else off. That is not a cover plate, btw, that is the axle. It's about 3 feet long, has splines on the end that you have to stick back into the differential, and it probably weighs a hundred pounds or more. Easy job for a truck shop, btw, and if you ever get towed, the tow truck driver will pull out an axle and put on a cover plate so the transmission doesn't spin while you are getting towed.

Edit: it actually looks pretty clean right around where the oil would be if it was the axle gasket. I might suggest getting a look at the back side of the wheels. If it is a hub, then it's a bigger job. It's not an super difficult job, it's just that everything is extremely heavy and the torque numbers are extremely high.

brian

Spot on ... ! I've had two axel hub seals fail ... the hub and everything around it is soaked before it makes it's way to the wheel where you can see it. I agree on the inner seal failure, not the axel hub.

And the right tools, jack, and stands cost a lot more than the labor rate for a shop that does.