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wheel hub lubrication
I was not sure how much lubrication goes into the fill hole on the drive axle. I assume it should be gear lube.
The present level is hard to determine depending of the position of the tire. How full should it be. The non drive hubs are easy to visualize but not the drive.
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19 Replies
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your picture to me appears upside down as the oil level looks right on….The lines on the face show full and use a flashlight if needed….
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Great picture of the non-driven wheel hub because it makes it clear where the fill level is on the steer and tag. As long as the oil is at that level the bearings will be lubricated. It should be noted that overfilling can make a mess so even though it is very difficult to see, the oil level should just barely show up in the bottom of the clear section just up to the ring.
For those who have replaced caps or gaskets and have to refill a hub be aware when filling the oil added will move slowly through and past the bearings so after adding hub oil wait for it to flow past the bearings and into the center of the hub housing.
The drive axle oil level is checked at the differential from beneath the coach. It should be checked routinely at every service, more often if a leak is detected. For those who will do their own hub seal replacement be aware that after a hub has been removed and replaced it needs to be refilled and the bearings need to be lubricated. A dry bearing in a drive axle can generate enough heat in a very few miles to weld itself together and twist the end off the differential. Mechanics will often prelube bearings with high temp grease or tip the entire differential toward the hub to get differential oil to flow into the hub.
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Thanks. I agree the non driven wheels are where they should be with the proper oil level. How exactly would I add oil on the red cap if I needed to do that? Does the cap come off or do you add via the four holes in the center.
On the drive axle the bolt at the top. What is that for? I assumed it was a way to check and fill or is that something for service people only. Possibly a vent when lube is added from below to insure filling ?
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When we got home from Petoskey last Monday I noticed smoke emanating from the left tag area. Having smelled plenty of over heated brakes in my life, I knew it was not that. It was hot oil.
In April, at home, I noticed oil had accumulated on the garage floor mat where the left tag sits. An easy diagnosis. So I swapped in a new hub seal. For the next two days I was filling that hub until it no longer drained below the full line. Thought I had it full. But apparently not. Gear oil does not flow easily in Chicago in April. I added another pint of oil to get to the full mark last Monday. The lesson for me is that when I replace a seal, and I think it is full, check it again after a heat cycle.
I’m also checking that the hub adjustment nut is not too tight. And the oil level in the other three non drivens.
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There are two types of non-driven wheel hub caps and the one shown gets filled via the the center hole plugged with the red cap. Usually your fingernails can pull the red plug from the cap. Make sure the tiny hole in the cap is open (a sewing needle works good) because that is how it breathes.
A second type of cap has an allen screw type plug for filling and I think a second one for draining.
I don’t know what the plug in the drive axle was for unless it was there to insure the hub is full after servicing the seal. The problem is if it is there for that purpose you can add a lot of gear lube oil at that point when all that is needed is a relatively small amount to lube the bearings. The excess will drain back into the differential and you have no way of knowing how much.
Dan emphasizes the care that has to be taken when refilling a hub. As I mentioned the oil slowly seeps past the hub bearings so you have to be very patient when refilling. I do not advocate driving to warm it up so oil will flow easier because you run a risk of lacking sufficient gear oil. In my filling I have “overfilled” the initial addition of oil, and then waited until it all flowed past the bearings. Then repeated that. If I over filled I could suck out excess with a turkey baster.
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“If I over filled I could suck out excess with a turkey baster.”
Jon, remind me to politely decline any invitation from you for Thanksgiving dinner.
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Les, have no fear. Di guards her kitchen tools as well as I guard my shop tools and my turkey baster is mine and mine alone and nobody, even Di is allowed to borrow it.
Mine looks a little worse for wear, hers is nice and shiny stainless steel so there is no fear of a mix up.
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Today discovered that the oil I added to the left tag hub leaked out. So maybe in April when replacing the seal, I did fill it with oil correctly. Possibly I did not set the adjustment nut tight enough to be in spec, i.e. 01” to 10” play/runout. If the runout is more than spec it would make it difficult for a seal to do its job. So I get to do it all over again. We did run about 4000 miles since the April seal swap.
In the past, we have discussed how some seals enjoy a long life while others not. The difference could be related to the hub adjustment nut.
This time also going to replace both bearings and races.
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I may regret saying this, but so far I have replaced at least 6 seals over our 28 years of ownership on three coaches, and none leaked. However I think this was due to four things. First, the surface on which the seal rests on the axle or spindle is perfectly clean. It will not seal if there is anything preventing the inner hub seal from making perfect contact.
Second, before I slide the hub back in place I make certain the inner portion of the seal rotates freely within the outer portion of the seal that is seated in the hub. When installing the seal if during the process of pressing it into the hub it is distorted and pinches the inner portion of the seal so it does not rotate the seal will fail.
Third, I make pains to insure as I replace the hub the hub and spindle or axle are perfectly aligned so as the hub is slid into position the seal is not sliding on to its mating surface at an angle or is not centered. I use a floor jack or some means of positioning the hub so alignment is perfect and rely on the bearings to keep the hub centered and aligned.
Finally I make every effort to comply with the spec in the service manual for the tightening of the hub nut. Too loose and there is play, too tight and bearings can heat and possibly fail. Prevost has two specs, one being to measure runout, or the other being to apply a specific torque value. I do not know why there are two different specs.
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Thanks for those thoughts Jon. The manual for mine says to tighten to 100 ft lbs while rotating wheel in both directions to seat stuff, then loosen, then tighten to 50 ft lbs, then loosen one third of a turn, and done. Yes I too use the floor jack as a dolly to slide the hub off and on being careful not to molest the new seal.
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Oil filled wheel hubs were used on Prevost coaches for many years. They were basically truck style caps for axle ends. They were meant to be used with no coverings over them so that the heat created by the wheel bearing turning and any braking action would be dissipated out by the wind going by and via the small hole in the rubber plug that Jon mentioned that release the pressure. With most motor homes they have nice wheel covers that fit over these oil caps. This in turn cuts down the amount of cooling that can be had via the air going by the wheel hubs as you go down the road. Plus you also have any type of heat generated in the oil by the wheel bearings and by the breaking actions that is also trapped now inside the shinny covers over the oil hub and fits on the wheel. What we have done for many years is to tell people to feel these oil caps only to the FILL mark not the FULL mark. This allows a greater area of expansion for the oil as it’s heated by those actions of the wheel and brakes. It may still under a normal hot day with a long braking action cause some oil to be vaporized out of the oil cap. Eventually you see it coming out from underneath your stainless steel wheel caps. But if you maintain a lower level you will not have this happen as often and as severely as it will happen with the oil Filled to the full mark and then covered with the stainless steel wheel cover.
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Excellent explanation.
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It it a good Idea to drain and fill regularly and is synthetic oil better to use? Mine are not leaking and oil is at a good level, should I take allen screw out drain and re fill with synthetic 140 w oil ?
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I looked up the maintenance requirements for your vintage coach and it is silent on wheel hub oil service intervals.
In fact it never mentions them as something to check.
The differential oil change is scheduled for 100,000 miles so maybe that is a good service interval for hub oil service.
https://techpub.prevostcar.com/en/download?id=150&type=manuals_operator&mode=view
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That’s one of the 1st things I did was a dif oil change.
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