Wheel hub oil level?

This topic contains 14 replies and was last updated by larry-2 11 years 1 month ago
August 6th, 2010 2:11pm
I have a peterbilt 335 [img]https://www.mechanicshub.com/media/kunena/attachments/legacy/images/wheel_Hub.JPG[/img] on the farm here and I noticed the front wheel hub was sweating a bit of oil out of the rubber plug on the cover etc. I got to checking the level and was wondering how much goes in this style. By the pic I'd say I'm at the min. level. Dealer said on the phone it was probably over full. Truck is new with less then 20,000 miles.

August 6th, 2010 10:21pm
make sure the little hole in the middle is clean, they are known for plugging with dust and that will build pressure, and blow the oil out or leave a sweat mark.
August 7th, 2010 3:41am
Good call on Mark22's part. Straighten out a paper clip and poke it through that hole.

Over full doesn't make sense. Spinning will force the fluid away from the hole. It's unlikely you filled it to a level above the hole! Sounds like the dealer is saying "Go away it's not my fault"!
August 7th, 2010 4:57am
Where abouts should they be filled to or is where it's at about right?
August 7th, 2010 3:47pm
the line above the minimum is fine, when the truck has sat for a bit is fine. That will be more than enough for the splash lubrication.
August 9th, 2010 10:00am
do you guys prefer oil hubs to grease hubs? In the military we changed all of our tanks to grease hubs. I think i remember someone saying that grease was better for the hard use we were butting the hubs through...
August 9th, 2010 11:17am
I had a fleet job where we used a really thin grease or a really thick oil, which ever way you want to look at it. The theory being it would be more forgiving to technician mistakes. I doubt the theory.

I might see a military advantage as in an off road enviroment if you break the hub cap the oil will run out. With grease you could limp home. In an over the road operation oil will make it far easier for the driver to do a proper pretrip inspection.

Whatever you do DON'T mix 'em! the lubricating properties of the grease will wear out but will seal the bearings keeping the oil from getting to them.

More important than what you use to lube them is do the job right. There may be a million opinions on how to set the preload. None of them are wrong if it gets the job done right. Where most guys screw up is they just wiggel the tire and call it good.

It takes all of about 30 seconds to slap a dial indicator on there and verify proper endplay. An awful lot of guys will say they can tell. Forget the argument about where do you get your arms calibrated, if you're dealing with a steer how do you tell the diffrence between proper end play and king pin wear if your not measuring.

If we were getting the job done right by the "I can tell" method the industry would not be trying so hard to take the tech factor out of it. IE: unitized hubs and preset bearings.
August 9th, 2010 10:47pm
I worked fleet, we followed Stemco torque set up for wheel bearing end play. I would always put a thin film of silicone on the outside of the seal, and a thin film of grease on the sealing surface on install. It always gives you the proper end play, and the star lock will always line up. It also gives you a confidence with all the hype over tires being lost on the road. Tightening the outer lock nut takes away from your end play when it jams up against the inner nut so when you think you have too much end play on the setting of the inner nut, it can be deceiving until the outer is torqued into place.
August 10th, 2010 5:44am
The only factor not talked about yet is how heat changes things. Oil will expand about 7 to 8% in volume from cold to hot conditions. Air, however, will expand about 20% from cold to hot.

What that may mean in your hub is that the oil level will change slightly when you look at the lines on the hub cap. However, as the air also expands, and the vent hole did not let the air escape, pressure could develop high enough to show seal leakage. This is why the vent hole is there.

If oil were splashed or ran down into that vent hole, it will be expelled and show the weeping that you see on the cover. A slight bit of weeping is normal. The more times that the hub is cooled and brought back to running temperature, the more the air and oil expand and contract, and the more the weeping can be evident. Conversely, a truck always on the road will have its hubs always at a relatively constant temperature and not show any weeping unless there is an actual leak.

As KN16 pointed out, bearing adjustment is important. The steel in the hub also expands as it heats up. This is why you need to have that proper amount of clearance for those bearings. Too tight an adjustment, the bearings experience excessive pressure as heat causes the hub to expand. This, in turn, causes more heat and bearing wear.

Too loose an adjustment will also causes excessive bearing wear; occasional steering looseness feeling; and can cause disc brakes to have longer pedal travel.

So, you are right to be concerned about seeing oil on your hub, but it sounds like this case is not a problem when you have the facts you need to make a decision.
August 12th, 2010 3:45pm
i agree with KN16 on the grease compared to oil question.
August 14th, 2010 5:40am
grease is great in heavy duty applications and where water intrusion is a concern, however for straight highway application, oil is a much easier way to go. A driver can make a quick visual check to ensure a proper oil level, and if end play is set correctly, its not uncommon for the seal and oil to last until the next set of shoes are to be installed. it has been my experience that any bearings run in grease seem to be neglected a lot more often. Just look at how many boat trailers you see along the highway after a long weekend.
August 27th, 2010 9:45pm
Don't know why I didn't think to mention this... Under "Tricks of the Trade"" I've got on entitled "Training it's good, It's free, Do it!". Switch the view to "most popular" it should be in the top 10. Any way one of the sites mentioned is ConMet PreSet hubs. There's a course offered on line or by CD:


You can also sign up for their quarterly email newsletter which usually has some good tips. Back issue PDF's are available back to 2004.
August 28th, 2010 10:04pm
Working on transit buses that put a lot of miles on oil is better than grease. Greased bearings require to much maintenance. Oil hubs run until the next brake reline, where M.A.N. axles require you to repack the bearings every 50,000 miles. I agree grease is great in military equipment because of the more durable hub cap etc. High milage equipment (buses, highway trucks) though should run oil. Transit buses used to run greased bearings front and rear when the oil seal technology wasn't the best. problem was the bearings needed constant maintenance. Spun a lot of races and changed a lot of rear axle stub shafts because the grease wasn't as good as it is today either.:woohoo: :woohoo:
August 30th, 2010 6:20pm
Well after I took the rubber cover off the hub there and blew and cleaned it off it seems to have stopped sweating out oil. Must have been what someone mentioned the little breather hole had gotten plugged.

February 6th, 2011 8:51pm
If you use the proper oil in your hubs it is always better than grease. with grease you have no way of knowing if your inner barring is getting lubed. With oil if you can see it in the hub you know it is getting oiled. When it is cold out what is grease like its almost solid. Take the time check seals and use oil.

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