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When do I lift the tag axle & dump air?
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Jim & Chris,
Do you guys lift the tag often on our sister coach? Maybe because we are only
a 40 footer, I don’t think I need to lift it.
I ordered my replacement clevis yokes from Prevost : 640130 YOKE, BRAKE
CHAMBER
I also ordered my missing drum retaining screws: 620040 SCREW, DRUM
RETAINING
Still trying to determine if I can fit a 22.5 X 90 steel wheel on the insides.
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On my coach the clevis pin rusted and froze to the bell crank, when i lifted my tag the pin would not rotate the small amount that it needed to and broke the clevis and it looked exactly like the pics in this post. Our Canadian winters with road salt can be hard on these type of parts. Now when I grease I put gob of grease about the size of three pumps of the grease gun and push it into the gap of the clevis around the pin. Problem prevented.
Herb
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If I recall correctly lifting the tag does disable the tag brakes, but at about 15 MPH the tag axle will drop and all brakes will again function.
On my 2014 X-3, the tag remains up until the lever is pulled. A beeping from the dash starts at 15mph as a reminder to lower. When I met with Prevost I was told the auto lift/lower feature was a chassis option and geared towards commercial models.
And yes, I’m a lifter on every forward moving 90-degree turn. Why? Not only was it recommended by Prevost as a good practice, out of respect to the parking lot owners, I don’t want to be the one who marks up the parking lots.
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Harry,
I have seen a sign in a campground in Murphy NC that says “raise your tag axle”. I am guessing the reason is there is a somewhat tight turn in this campground and the campground wants to avoid skidding tag tires and eating the pavement up. Other guess is that Harry G is just having fun in his backyard. I lift my tag when making a very slow speed sharp turn (like backing into my parking spot or a campground space or leaving that campground in Murphy NC).
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While this may not be the total answer relating to the 365 tire decoupling groove tears, lifting the tag on sharp slow speed turns may help avoid or prevent the problem.
But remember, on our longer coaches with considerable overhang such as XLII coaches lifting the tag will drop the rear and before lifting the tag make sure that drop of the rear of the coach is not going to cause a bigger issue, such as a dragging hitch on the ground such as what might happen if there is a sharp incline like a driveway. You do not want the weight of the rear of the coach to be pushing on the engine cradle.
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But remember, on our longer coaches with considerable overhang such as XLII coaches lifting the tag will drop the rear and before lifting the tag make sure that drop of the rear of the coach is not going to cause a bigger issue, such as a dragging hitch on the ground such as what might happen if there is a sharp incline like a driveway. You do not want the weight of the rear of the coach to be pushing on the engine cradle.
That sounds like a good reason to get an X-3.
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Working on the broken yoke today, squirted all the fittings I could see just because.
Brake chamber that lifts the tag is leaking. I thought there was not supposed
to be air there unless the tag lift switch was flipped. Does this mean I have
two leaks, one at the fitting on the brake chamber and the tag lift switch?
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There should not be air at the lifting chamber unless you are lifting the tag.
The only time that should see air pressure is when the air from the drive axle air bags to the tag axle air bag is blocked and the tag axle air bag air is being exhausted.
Something is messed up.
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Wow, what a surprise on my 2000 Marathon with no service history that something is screwed up.
Here are pictures of the two norgrens at the drive axle.
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All compression, very good.
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Working on my tag lifts this weekend. Replaced the #36 brake chamber that lifts the tag axle. I think I have figured out why I have broken three clevis yokes and two brake chambers and two pivot arms in two years. When my TW-1 switch for the tag lift is “down”, I have air pressure at the tag lift brake chamber. The push rod is fighting the tag air bag which has air pressure too. When the TW-1 switch is flipped to “up” to lift the tag axle, I have no air to the tag lift brake chamber and the air is dumped from the tag axle air bag and the tag up tell tale light is on at the dash.
My understanding of the TW-1 valve is air is supplied at the bottom, and the flip lever either lifts or closes off the plunger to let air pass through to the delivery. Could this be hooked up incorrectly? How does the tell tale light know to come on?
The norgen valve for the tag lift is really difficult to get to. As evidenced by the terrible picture. It appears to have the supply into port one and delivery split out to right and left on port two. I believe this is the correct configuration. I installed a temporary shut off valve before the tag lift brake chamber. I can keep the valve closed and not lift the tag axle, without damaging the brake chamber or the yoke or the pivot arm until someone figures out what is backwards.
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John,
I know Prevost has made running changes to the suspension system so I would suggest your first step to resolving this is to pull up the pneumatic diagram specific to your coach.
When you lift the tag via the lever to the left of the driver’s seat you are actually doing a few things at once and the three Norgrens mounted on the frame up over the tag axle all come into play.
The tag lift lever first causes the Norgrens between the drive and steer axles to shift so the open path between the drive and tag air bags is closed, locking air into the drive air bags.
When the path is blocked it opens the path from the tag air bags to the exhaust tube hanging down from the 3 port Norgrens and air pressure in the tag air bags drops to zero.
At that point the tag axle lift chambers are pressurized, while simultaneous with that the brakes on the tag axle cease to function.
My guess is the Norgren that supplies pressure to the tag axle lift either has the 3/8 hoses reversed or in the wrong position on the valve, or the 1/4 hose to the pneumatic operator on that Norgren is pressurized when it should not be.
The situation should be taken seriously because there is the potential that as long as this situation is present your tag axle brakes (service) may not be functioning. The key is the sometimes difficult process of tracing hoses or connections to Norgrens to determine what is messed up.
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