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Author Topic: what a difference a weekend can make  (Read 5284 times)
John Z
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« Reply #15 on: June 07, 2007, 06:27:34 PM »

Thats quite an interesting idea about using the tire monitors as a warning device. I am sure the tire pressure was up enough for them to sense the increase. Probably could have saved some damage depending on the timing of the air pressure increase.

Well, i am feeling better after reading through all the input from you guys. After shopping for and buying towing insurance, and buying new fire bottles, i will bring it in and have the bearings on the other 3 corners checked. Certainly do not want to ever go through this again.
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« Reply #16 on: June 07, 2007, 06:41:39 PM »

A a 4104 owner this post got my immediate attention.

Lee's post is very informative and answered a bunch of questions I was going to ask. It is still hard for me to believe that those axle nuts can come off if they are properly torqued and have good lock washers, but obviously Lee has experienced this very thing.

I inspected mine right away and discovered that each rear axle has two studs about 3/4" longer than the rest but aren't in the same positions on each wheel? Does this extra lenght mean anything except that maybe someone has replaced them and didn't have the shorter studs?

I will now be sure to check the torque on both axles but this probably won't mean much since they have probably been installed for years.
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kyle4501
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« Reply #17 on: June 08, 2007, 05:19:07 AM »

. . . It is still hard for me to believe that those axle nuts can come off if they are properly torqued and have good lock washers . . .

You would be surprised at how much the loading on the bolts can change with a small misalignment.

In Lee's scenario, the axle nuts were loaded way above their limits when the bearing failed. Once the studs stretched, the preload from the initial tightening was gone.

The nature of the rotating cyclic loading will encourage the nuts to loosen as the bolted parts 'walk around'.


I have found that sometimes the studs weren't properly installed in the hub & that's why they stick out farther than the others. I have also found some studs to be longer, so you might need to check on that the next time you have the axle out.
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« Reply #18 on: June 08, 2007, 08:46:05 AM »

Thats quite an interesting idea about using the tire monitors as a warning device. I am sure the tire pressure was up enough for them to sense the increase. Probably could have saved some damage depending on the timing of the air pressure increase.

Well, i am feeling better after reading through all the input from you guys. After shopping for and buying towing insurance, and buying new fire bottles, i will bring it in and have the bearings on the other 3 corners checked. Certainly do not want to ever go through this again.

Having the wheel bearings inspected and adjusted correctly is something all of us busnuts should put on our list of things to do if we have not done them during our ownership. We have bought used buses with who knows how many miles on them and how long its been since the bearings were last serviced. This on my list for my Neoplan before I make any long trips.  I just found out my bus has a factory rebuilt 8-92, last night while replacing a manifold gasket and exhaust elbow, dated 1999.
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« Reply #19 on: June 08, 2007, 12:59:45 PM »

My Dina needed to have all of the wheel bearings replaced when I got it home.  I believe C&J also replaced the races on some or all of them.

JD said I was lucky neither of my tag wheels came off on the trip home.  He showed me one of the bearings and it was badly pitted.
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« Reply #20 on: June 08, 2007, 01:35:43 PM »

Just a thought, what if the prior ownner at one time had the bus towed & removed the axles to prevent the rearend from turning the automatic transmission and reinstalled the axles and not tightening the axle nuts. A long shot.  Ray
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« Reply #21 on: June 08, 2007, 02:01:11 PM »

That is a possibility but if the wheel bearings run in rearend oil/grease you will have a mess on wheels you can't miss and if they use wheel bearing grease it would probably shear the studs/bolts before the wheel bearing failure and brakes overheating enough to explode the tires.
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NJT 5573
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« Reply #22 on: June 08, 2007, 02:11:58 PM »

I think those bearings are oiled with differential gear oil, Is it full? Lee's scenario sounds good, but to be safe, a fryed wheel bearing may be secondary. Maybe the shoes cammed over and stuck or it has piggy back spring brakes and a blown emergency diaphragm. Having a brake hang is not normal, especially after it cooled down and the first mechanic had put the axle back togather. You can use a hand held temp probe to shoot thru the wheel hole and get a drum temp and you should watch that real close until you are sure the problem is solved.
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« Reply #23 on: June 08, 2007, 08:34:52 PM »

Those bearings can be either grease or oil, depends on what a PO wanted & what seals were put where.

Bearings go bad every day. The bearing life charts show life of 99+% of the bearings. That means some won't last that long.

If one of the bearings went out, the axle would hold the hub straight while the bus was jacked up But once full weight of the bus was put back on it, the axle will flex & allow drum to hit the top inner & bottom outer edge of the shoes.

There was a problem when the mech jacked up the bus & turned the wheel by hand (- with difficulty that should have told him something's wrong), but bus wouldn't roll when let down.


Complicated machines often present complicated symptoms of a simple failure.
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« Reply #24 on: June 08, 2007, 09:03:05 PM »

I don't think any rear wheel bearings are intentionally oiled with differential oil. I have a bunch of older large trucks and none of them use this system and I have never heard of this system. It may be because the gears and bearings use much different kinds of lube oil.

This has come up numerous times before and from my experience the only time diff oil gets into the wheel brg is when the seals fail, then it oils the brakes and messes up the wheel.

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« Reply #25 on: June 09, 2007, 05:45:48 AM »

FWIW, my 1963 International tandem axle dump truck has Rockwell axles & the wheel hub shares oil with the axle. There is only one seal & that is between the OD of axle tube & ID of the hub. I'm sure there are other styles out there. . .
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« Reply #26 on: June 09, 2007, 08:26:21 AM »

I've been in the trucking industry for 30 years, and until I got involved with buses had never heard of a rear axle that was oil lubed with grease bearings on the ends.  I personally have never seen that setup until now.  99% of the trucks I've seen use the gear oil to lube the end bearings.  When I bought my bus, one of the first things I did was to change the front grease bearings to oil for better high speed cooling (virtually all trucks are oil lubed-some trailers have sealed grease bearings).
As to using the tire monitors to detect over heating (I have them on my bus), the only way you could tell you were getting higher pressures maybe caused by higher heat would be if you were constantly pushing the button to see if the pressures had changed since the only time the alarm is set off is when it detects a low pressure situation.  Good Luck, TomC
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John Z
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« Reply #27 on: June 09, 2007, 08:52:46 AM »

Wow. Lots of good posts here, certainly a lot to think about. One of the thoughts that keeps rolling around in my mind, is maybe to switch to the oil bath bearings when i have my bus checked out. How complicated and expensive would this be to do?

I am not familiar with how the oil level would be checked, but this sounds like it would be easier to chk and keep an eye on that pulling it all apart to chk on a greased bearing.

I am not sure about doing this on the rear axle, as if the diff is leaking, then wouldn't the bearings be running dry? I am not sure what the level of the oil in the diff is compared to the tubes and if it would reach the bearings or not. I imagine some sort of level check on the oil system, and that does seem workable to me.

The second mech told me the s-cams, anchor pins, adjusters were all in good shape. So he was quite certain it was a bearing failure.

Everybody get out there and chk those fire bottles though. I had one that the gauge said was good, but it did nothing when i tried to use it.
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« Reply #28 on: June 09, 2007, 10:45:40 AM »

Bearings need to be in a perfectly clean lubricant and environment.

Are you sure no grindings contaminated the area near the bearings?

There are many brands of bearings, some from overseas.  They may be acceptable, but my experience has led me to specify only Timken.

I know Japan has the capabilities to grind very close tolereances.  If there are any bearing experts with experience of other brands, please reply. 

Ed Roelle
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gus
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« Reply #29 on: June 09, 2007, 04:51:48 PM »

I have a '31 Chevy 1.5 ton dual wheel flatbed, a'42 GMC military 6x6, a '52 GMC 6x6, a '60 White WC22PLT dump(Originally a tractor), a '70 Dodge C900 tractor(230 Cummins), a '59 ALF fire truck(Cat diesel) and a '71 Ford WLF fire truck. I also had a 2.5 ton Reo military 6x6 with Rockwell axles. All these trucks have GMC, Dana or Timken diffs.

These are all heavy duty except the Chevy. None of these trucks use differential lube on the wheel bearings.

The military trucks specifically caution about letting diff lube into the bearings because it washes out the grease. Of course these trucks are built to drive in rough terrain so, supposedly, one axle could be starved for diff oil on the side of a hill.

I realize that oil hubs are different, but I'm only talking about differential oil.
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