Wheel bearing oil baths

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Jan 13, 2005
I know that some forum members have oil bearing baths on their front hubs, while others have greased bearings. I heard one guy say he'd converted his front hubs from grease to oil bath. Has anyone done this? Is there a kit that you buy and is it something you can do yourself, or is it best done by a chassis service shop?
On the other hand, what is the advantage of the grease over oil bath ??? ??? Why bother converting?
caltex said:
I will add another question to Tom's - what are the advantages of the oil bath?

Hi Robert,

I would guess the advantage of oil hubs is the ability to see the lube. The hub has a clear fitting with a level line so you can observe the amount of lube. Remove the rubber cap and fill to line.

One problem is some manufacturers put a chrome cover over the opening which makes the wheel look nicer but covers the site glass. Some owners don't even know they need to check it!

Hi Jim,  I was thinking that maybe the oil bath would give less friction (not that that would matter on a 30,000 pound motorhome) or longer bearing life.  But now that you mention maintenance, how often do the front bearings need to be repacked for a non oil bath axle?
Hi Robert,

I really can't answer your question since I have the oil bath. Perhaps someone else has the greased bearings.

Phil said:
Not that it would happen in our group ;D but, some people like to have "things" added to stuff they own.

Phil, my question was a serious one. Our coach has greased bearings and I know some folks, including Jim, have oil baths. Someone in one of the seminars this week explained that he had changed his greased bearings to oil baths. When I asked why, several folks laughed (as if I should have known the answer) and the guy said it reduces friction and eliminates the need to re-pack the bearings. I do most of my own maintenance on the coach, but I'm not about to remove wheels to check & re-pack bearings. I'm just trying to understand if this is something that can be installed aftermarket and if it would eliminate one headache or substitute another.

I think the chassis manufacturer would be able to advise you on this as well as cost to do so.  I have heard of it being done but have no details such as chassis etc.  It might be expensive but off hand I don't really see any reason is can't be done.


The chassis manufacturer is Monaco's captive plant in Wakarusa, IN. I'll ask the folks here in the OR service center to see if I can get some info, but they seem to be geared more to repairs than modifications.

>> Has anyone done this?<<

I believe Ken Kuch did his, since he has a Monaco too I guess it would be no problem for you.

At John Day Dam, OR
Thanks Terry. I'll keep an eye open for him.

I prefer to gather more information before determining it's unnecessary. I really have no idea what it would cost and haven't yet been able to verify if there's a benefit or a downside. But the idea of being able to look at a sight glass daily or after every trip vs having to remove the wheels and hubs to know if my bearings have sufficient lubrication sure sounds appealing. This is not a case of 'mine is better than yours' because I don't have them, nor is it a case of buying an add-on just for the sake of it. I'm just trying to figure out if it's worth making the change.

Some changes/upgrades I've made to our coach have been very definite improvements and not just because I made or paid for the changes. Some I've yet to make, such as one or two slide-out trays and a tire pressure monitoring system, will also be worth the money. Other "improvements" I've passed on for one reason or another. I don't make changes for the sake of it.

Because we bought the coach off a dealer's lot rather than order it, we were somewhat restricted in factory-installed options. As I hear about after-market alternatives to the options we didn't get, I like to evaluate them and ask for input from others. Your negative vote on the oil baths is noted, although it's not clear if you have an informed reason for it. If so, I'd sure like to hear it so it can help influence my thinking.
Phil said:

My answer was very serious.  I believe that most add on stuff is not necessary.  Some people however will swear that the add on stuff is better than the original equipment.  I am not going to change my wheel bearings to the oil bath. 

Ya pays yer money and ya takes yer chances.



Oil bath bearings are not necessarily add ons. Both my Country Coach and American Dream came with oil bath bearings as standard.


I agree that one should not run out and replace stuff indiscriminately with "new stuff" but do feel the oil bath bearings could be worthwhile as long as the cost isn't prohibitive. As pointed out it's much easier to tell the bearings are being lubed than with grease. Also fairly inexpensive to change or top off when necessary.

Phil said:
My comments are not against oil bath bearings.

Glad you clarified that Phil because the topic you replied to and the message you quoted both specifically referred to oil bearings  ;D

I was commenting on replacing "stuff" that came on a rig with "stuff" that some believe is better than original equipement.

I'm slowly replacing some OEM equipment (aka stuff) on our coach and adding others that weren't there to begin with. I believe that, when I'm done, I'll be financially better off than if these options (replacement or additional) were ordered with the coach. Meanwhile, I bought the coach off the lot and didn't have to wait for it to be ordered and built. Hopefully you're not against genuine improvement or saving money  ???

Monaco actually offers oil bath bearings. Its a non-listed option. I don't think there is a cost difference.

I had the bearings on my Windsors converted after the first year, ie. when they were do to be repacked. I think the cost was $225 which was only a little more than repacking the bearings. The work was done at Kaiser Brake in Eugene. The bearing themselves are not changed. The grease is removed, the inner seal is changed and the oil bath hub is installed. Monaco Service recommended Kaiser. The only down side I see is if the inner seal fails you lose the oil.

Monaco Corp favors greased bearings but gave me no reason. Kaiser Said greased bearings are better if the coach is going to sit a lot and oil is better if the rig is in motion most of the time. At the time I converted we were full time in the coach (I was working as a consultant in manufacturing). Now the coach sits for two months at a time. I checked with the local Freightliner shop and they said they saw no problem with the oil bearings based on my current use. My first coach, a HR Imperial Diesel was on a Spartan Chassis with Oiled hubs and it sat in storage from October through mid february when we would usually head to Florida (from Vermont).

If you convert, watch the oil level for the first few days. I added oil at the first two stops on one side and the first four stops on the other side. I called Kaiser and was told that was normal and that the tech should have advised me. The tech did tell me to get a some gear oil and to check the bath the first few days, but he did not tell that it would be normal to add oil.

Let see $225 once (conversion) or $200 annually (repack).

Thanks for that Ken. Wish I'd read your message before left Coburg/Harrisburg this morning  :(

Ken & Sheila said:
Monaco actually offers oil bath bearings. Its a non-listed option.

That's nice to know for if/when we buy another Moanco.

The only down side I see is if the inner seal fails you lose the oil.

That's a concern that's been in the back of my mind. If all the oil leaked out the bearings would be shot. If they needed repacking, there would probably still be some grease in there.

If you convert, watch the oil level for the first few days.

Thanks for that warning.

Let see $225 once (conversion) or $200 annually (repack).

Sure sounds like another good reason to convert. More like a no-brainer.

Thanks again.

>>The only down side I see is if the inner seal fails you lose the oil.<<

OOPs, there is another one!!  IF you lose the seal while driving, you will probably have to replace the brake pads too.  I was fortunate that my seal gave way in the driveway so only the seal and oil needed to be replaced.  It was still pricey!!  I believe it failed because it had been overfilled and on a very hot day, the pressure caused the oil to release through the seal.  :-((
Looks like Phil deleted his comments without any explanation.
James Godward said:
....my seal gave way in the driveway so only the seal and oil needed to be replaced.

That's one failure. Sure sounds like you were lucky it happened in the driveway Jim. I wonder if others have had similar failures.

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