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Driving with tag axle up
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Some folks swear by grease, and others oil?
My experience has been flawless w/oil. We’ve had 4 tag axle MHs with oil/wet hubs on the steer and tag axles. None have ever leaked or had a bearing or tire problem.With that said, nearly 2 yrs ago, while I was under the bus, I luckily found a drive axle hub inner seal that was beginning to leak. I changed both sides.I never raise my tag. But in your situation I would. -
The seminar in which Prevost discussed the features of the tag axle lift was about 25 years ago. Some of the techs now working on these coaches weren’t born yet. Those that might have been working on the coaches back then probably forgot that feature.
When the tag axle is lifted the brakes are disabled and I presume at the time compromising the brake system was not frowned upon by the department of transportation, and tag axle brakes were only service brakes. I do not know why or when the change came about to allow the tags to remain lifted but it may have to do with the fact at some point Prevost started using combo brakes like on the drive axle.
As to any service on hubs and bearings and seals one, I have never seen a Prevost with grease lube instead of oil, and two, I have never serviced a hub or bearing without first using high temp grease on the bearing, and then refilling the hub reservoir, tipping an axle if needed to insure bearing grease or oil is in the hub. I know two Prevost owners that had hubs serviced and the shop doing the work failed to insure the bearings were greased and the reservoir was at the proper level and both coaches ended up with seized bearings and the axle end broken off within 4 miles. One was on the Tampa bay bridge.
1999 XLV X-6872, liberty #440 -
Again, thanks for your comments and experiences. Like Don said, i never drive with my tag axle up. i know they recommend raising them when you’re parking and making sharp turns, but usually i forget. So, my tag is almost always down. On the recent occasion though, i was glad i could raise it sufficiently.
Question, do new Prevost coaches come with oil/wet bearings or grease bearings? If so, has it always been that way, or is it an option? After my recent problem, i’m a little cautious about oil/wet bearings. Probably shouldn’t be though. But it seems it is something you have to check regularly. Grease bearings just appear to be more trouble free. What are most of the older coaches running now?
Thanks,
meslundy
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Something else. There may not be too many people on this thread, but i think this is a very important topic. My guess is, more coaches end up on the side of the road due to tire, brake, and axle related problems, than any other. A good friend, and Prevost enthusiast, once told me more coaches catch fire due to tire fires than any other cause. Don’t know if that’s true, but is seems possible. As long as a coach engine and transmission are serviced regularly, they seem to be pretty much trouble free, but the tires, brakes, and axles, take a beating everytime your out.
meslundy
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Current production coaches and going back to at least 2005 chassis years the hubs are sealed bearings. There is no service possible or required. If they make noise or are loose they need to be replaced.
I do not know how to determine the root cause of fires or on the road failures. There may be statistics and data that can be used to arrive at an answer, but I have no clue how to find that info.
I do know from decades on Prevost forums owners and probably commercial drivers rarely do a detailed pre-trip inspection and just doing that inspection is going to identify potential issues. One common problem is low tire pressure. The tire pressure monitoring systems are invaluable in minimizing this as a problem unless it is ignored. But a TPMS without reliable temperature monitoring will not help with having other valuable information. A set of over greased brakes may not allow the brake discs on coaches with the Meritor disc brakes to retract. That will allow over heated brakes and other associated potential issues.
A poorly done hub seal replacement can be a serious issue with nuts too tight on the hub causing bearing failure. Prevost lists exactly how to torque the nuts as well as the specification for tightness. Not all mechanics believe the words in the shop manual and their “wisdom” has the ability to create serious failures.
Before TPMS became prevalent it was a good practice at every stop to use a IR gun to monitor tire temps and hub temps. Under normal circumstances with tire pressures set to the pressures listed in the charts based on weight a driver would see nearly identical temps on every tire and nearly identical temps at the hubs. As soon as one was found inconsistent with the others it became a sign of everything from a dragging brake, bearing failure or tire issue. Who does that anymore??????
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My bus is a 2005 2004 shell it came new with grease bearings and I love it so for. The original owner that had it built was in the in trucking business
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My 2005 has permanently sealed hubs and compared to grease or oil filled hubs it is fantastic.
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The wiring diagram for our ’96 shows a speed switch that feeds 24V ignition power to the tag lift switch, set for 20 mph. It’s on the rear wall of the steer bay on ours.
Regarding overloading tires, the ETRTO gives guidance on reducing speed and increasing pressure to increase load-carrying capacity. To get a 20% increase on a tire with speed rating L, you’d have to limit your speed to 30 mph and increase tire pressure by 25%. Driving 50 mph only offers a 10% increase in capacity and requires a 12% increase in pressure. This may be limited by the maximum pressure rating of the wheel as well. On our coach, we’d be above 20% overloaded with the tag raised, considering the weight on the tag and the load removed from the front axle by effectively shortening the wheelbase.
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Interesting comments on sealed bearings.
While I’ve had no issues with my steer or tag bearings, I have had issues with failed oil seals on drive axle. Are the drive axle bearings sealed on the newer coaches? Is retrofit possible?
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No feeds oil from rear end
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Joel, seals should last forever. Over 32 years I replaced 6 and never had one replaced fail. My attitude was if it wasn’t leaking I wasn’t touching it. Seals I have replaced for others were doomed from the start because whoever installed them damaged the outer shell, which in turn put a slight pinch so the outer seal and inner seal would not freely rotate with respect to one another. They are fussy and installation has to prevent any pinching between the inner and outer seal and when the hub is installed on the axle spindle it has to be perfectly aligned both side to side or up and down or it can damage the seals. You may create more differential heat than others, but the seals should be designed to resist that heat.
Half of my leaks were on the drive axle but I do not know why the disproportionate failures would occur there.
Two of my coaches were at around 250,000 miles when sold and currently I am heading to 180,000 on my coach and I do not expect to see any failures.
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