Drive Axle Oil Splash

[ToyMan]

Arrived in Tempe Arizona yesterday and noticed oil splash coming from under the hub cap on the drive axle. I was wondering if a change in altitude or heat would cause oil to expand and come out the breather hole on the axle hub.

The last time it did this, there was a small amount of oil showing on the rim and I looked on the inside of the drive tires and there was no oil splatter on the inside of the tires.

I haven't looked under there yet to see if there is any leakage on the inside of the drive tires.

Below is a picture

[Jon Wehrenberg]

Ron,

Pull the hubcap and see if it is leaking from the gasket around the hub. If not it is likely a hub seal.

The differential oil level is barely up to the level of the threaded end of the differential where the hub is secured. The bearings in the hub depend on the tipping of the differential through normal driving to flow small amounts of differential fluid into the hubs to keep the bearings lubed. Excess fluid in the hubs just flows back into the differential. I doubt if expansion of the fluid is the cause for the oil stains and would suspect a hub seal is failing.

Look between the wheels and at the inside of the inner drive axle wheel. If oil is seen the hub seal needs to be replaced. If you do your own work this is a relatively easy job. If you take it for service a couple of hours of labor and $50 for the seal is what it will take.

At least two POG members have had the end of the differential at the hubs damaged, bearings ruined and the buses put on trailers as a result of dry bearings after hub seal replacements so be certain the hubs are filled with oil or the bearings are prelubed before driving the coach. With dry bearings you may be able to drive 5 miles before everything seizes up so it is important to be assured of lubrication.

Also, the insertion of the new hub seal is a critical part of the repair and if it is damaged, even slightly so the inner and outer portions fail to rotate freely the hub seal will leak. It is not a difficult repair but techs seem to screw it up.

[GDeen]

I just went through this excercise a few weeks ago. Backed out of the barn to go wash the bus, and saw a small amount of oil on the ground. Didn't see it on the walk around because it was between the dual drive wheels. Only difference was mine was running down the inner drive wheel. Did the same thing Jon is suggesting following the same advice from Steve Bennett. Pulled the cap and it was dry so I was faced with hub seal replacement.

I had Prevost FW do the work and talked specifically with the service manager about the procedure and which tech I was getting. I then watched him and asked questions of him to ensure it was done correctly. Having never done the job before personally, at the very least, they knew I was on top of what was going on and paying attention. No doubt that helps with quality of work in my estimation.

At the rally Bill Jensen pointed out something we all know about business. Standards may be set, training may be instituted, but you are still dealing with people. It pays to stay on top of them even if you believe that to be a waste of time and something that Prevost should be able to handle without supervision. I agree with that viewpoint, but the reality is somewhat different. Plus I enjoy the learning experience of watching them do the work.

I have found that if the techs see that you give a rats rear end about your coach, they are much more likely to also have the same attitude. If you make an effort to get to know them on a personal level, they may even do a few odds and ends, or point out other things to you without charge.

[JIM CHALOUPKA]

Ron, it appears you have a leak at the axle mounting flange. You will not find an inspection reservoir nor a fill plug as on the steer and tag.

There may be one or several nuts holding the axle inplace that are loose.

The axle is sealed with a gasket and RTV sealant on both sides of the gasket and sometimes you only find RTV sealant and no gasket.

The sealant should be around the studs as well as on the flat mating surfaces.

You may purchase the gasket from Prevost or make one of your own. I made my own as they were out of stock when I need one.

There are two sizes of nut in use. Torque values are for lightly oil lubed threads and from Prevost shop manual page 11-8.

The torque values for each are:

9/16-18 plain nut: 110-165 lbf-ft

5/8-18 plain nut: 150-230 lbf-ft

If you're not sure what you have use 150/165 lbf-ft

some pictures;




JIM

[Coloradobus]

Toyman, we have similar issues when changing altitudes, and Stewart Stevenson and Prevost replaced the paper seal a number of times. I asked how was the Diff Vent?? Response, looks good. Last year I had Prevost send me the 12 dollar part, put it on, re-torqued the hub flange bolts, and no more oily drive wheels. If you Diff Vent has never been changed, try it for a few bucks to see if it solves you problem

[ToyMan]

ColoradoBus - I cannot find the diff vent on CatBase. I want to look at the schematic. Do you have a part number?

Jon - Haven't had a chance to remove the hub cap or inspect the inner side of the wheels yet. Playing baseball here in Phoenix and have a double header today. Hopefully tomorrow since I only have one game.

Jim C - Thanks for the photos.

Hopefully, all this great info will lead to a solution before I head back to Florida.

[Jon Wehrenberg]

Ron,

It is not easy to see between the wheels or more importantly to look at the rear of the inner drive axle wheel which will collect the leak from a hub seal. Hope that it is the outer gasket since all that entails is popping the axle out and resealing it. If that is the problem post it and we can walk you through the fix. That can be done with nothing more than wrenches.

If the hub seal is leaking it is not the end of the world, but must be resolved when you get home. But first you need to get the bus over a pit such as at a truck stop and make certain the differential is full. If the bearings are not lubed properly bad ju-ju happens.

[ToyMan]

I took the wheel cover off and did not see oil coming from anywhere. The black substance looked like it was only on the outer edge of the wheel cover. My drive axle wheel covers came from Prevost and have a plastic lug nut cover that is threaded on the outside.The lug nut cover is placed on the lug and the bullet shaped lug nut covered is screwed on. I have never been able to tighten the bullets enough to make the wheel cover snug against the rim. They need another 1/8 inch to accomplish that.

The black stuff on the rim does not look like oil. It is real thick and pasty like it might be a mixture of water and rubber dust. It has no oil smell at all.

I looked between the wheels and on the inside of the inner tire and there is no oil anywhere. No slinging, nothing damp at all. The only moisture I saw was coming from the air drier on the passenger side near the drive axle.

[Jon Wehrenberg]

If your drive axle hub seal was leaking, the oil which leaked would mix with or get covered with the dust and dirt that gets picked up off the road plus brake dust.

If the leak is minor the resultant mess on the inner drive wheel will tend to be dry, but as the leak increases in size that dirt, dust, oil mess is visibly greasy or oily and is nasty. A leak free inner wheel just gets covered with brake dust and road dust and is bone dry with no signs of oil at all.

The slight leaks are rarely noticed until the coach is driven through rain and then the water picks up the greasy mess and makes it visible from the outside.

I would keep an eye on that axle and make sure the differential level is checked during maintenance and I would make absolutely sure someone ran their finger along the inner wheel to make sure the dirt is dry and that there is no grease or oil in or on it. Any hub seal leak will be contained in the low spot on the wheel rim.

[ToyMan]

Took the bus to Divine Coach Care (previously Desert West Coaches) in Phoenix yesterday. They put it over a pit and I accompanied the mechanic in the pit for visual inspection.

Everything under there was dry. Checked the differential oil and it was 1 quart low. They topped it off.

Also inspected the brake cannisters and they appeared new. Everything else under there looked good also.

When I removed the hub covers, the axle mounting flange appeared damp on the extreme outside but no major oil spillage. It appears that the oil is coming from there but in no great amounts. I will change the gaskets when I get back to Florida.

At least I now have the peace of mind knowing that my differential is topped off. As usual, I will walk around the bus every time I stop and do my visual inspection.

Thanks to all for advice and photos.

Ron

[truk4u]

Ron,

Did you make sure the vent was OK?

[ToyMan]

Tom,

Yes the vent was OK.