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Rear End Low [message #278102]

Wed, 20 May 2015 21:04

73 Canyon Lands 007

Messages: 2
Registered: May 2015
Location: Los Angeles

Karma: 0

Junior Member

After lusting after these gorgeous creatures for over 40 years, I finally bought one.

Rear end of the vehicle is very low. It seems to rise up somewhat when engine is running. What are the possible causes?

Thanks.

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Re: Rear End Low [message #278103 is a reply to message #278102]

Wed, 20 May 2015 21:10

habbyguy

Messages: 896
Registered: May 2012
Location: Mesa, AZ

Karma: 3

Senior Member

Welcome aboard... hope you have as much fun with your "new" GMC as the rest of us (I mean that in a good way, of course). Wink

That's not a problem - that's a feature! The air suspension is doing its job and bringing the rear of your coach up to (hopefully) proper ride height. If it's drooping too quickly when you park it you'll have to chase down a leak in the air suspension system, but I think you'll find that a whole lot of other GMC coaches droop over the course of being parked for a few days. Mine does, and it's not really a big deal to me (I let the air bags down and drop the rear end onto blocks when I park it anyway).

Mark Hickey Mesa, AZ 1978 Royale Center Kitchen

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Re: Rear End Low [message #278104 is a reply to message #278102]

Wed, 20 May 2015 21:12

Terrasmak

Messages: 40
Registered: December 2014
Location: Las Vegas

Karma: 0

Member

Leaking line to the airbags would be what I looked at first

Len Novak, 76 Eleganza II, Las Vegas

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Re: Rear End Low [message #278105 is a reply to message #278102]

Wed, 20 May 2015 21:16

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

Low air bag pressure. However, the GMC does not sit level, based on your eye following the belt line trim. There is a slight tilt to the rear of the GMC, everything being correct.
Sounds like your air bags have a slow leak somewhere, and when the engine is running and the air compressor kicks in, the rear end lifts with increased air pressure in the bag. Does it settle lower when the engine has quit running and the air compressor is no longer powered?
Does your air bags have both a cut-off valve and a schrader valve installed. This simple add-on allows you to add air to the bag with an inoperatiable air system.
Welcome to the cult.
Tom, MS II

2012 Phoenix Cruiser model 2552 KA4CSG

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Re: Rear End Low [message #278111 is a reply to message #278102]

Wed, 20 May 2015 21:44

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

73 Canyon Lands 007 wrote on Wed, 20 May 2015 21:04

After lusting after these gorgeous creatures for over 40 years, I finally bought one.
Rear end of the vehicle is very low. It seems to rise up somewhat when engine is running. What are the possible causes?

Thanks.

It should raise to be about an inch lower than the front when the dash switch is set in "travel" mode.

An electronic copy of the Operating Manual is here

http://www.bdub.net/manuals/ops73/X7321A.zip

An electronic copy of the Maintenance Manual (and the electrical schematics) is here

http://www.bdub.net/manuals/X7425/index.html

Lots of other manuals are here

http://www.bdub.net/manuals/

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Re: Rear End Low [message #278175 is a reply to message #278102]

Thu, 21 May 2015 20:53

73 Canyon Lands 007

Messages: 2
Registered: May 2015
Location: Los Angeles

Karma: 0

Junior Member

Thanks so much for all the excellent replies.

I have no manuals, so I am not sure if the air bag knobs on the dash are set properly.

Can someone point me in the right direction for them? And I will get the manuals.

Tks mucho grande.

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Re: Rear End Low [message #278177 is a reply to message #278175]

Thu, 21 May 2015 21:36

Dennis S

Messages: 3046
Registered: November 2005

Karma: 2

Senior Member

73 Canyon Lands 007 wrote on Thu, 21 May 2015 20:53

Thanks so much for all the excellent replies.

I have no manuals, so I am not sure if the air bag knobs on the dash are set properly.

Can someone point me in the right direction for them? And I will get the manuals.

Tks mucho grande.

Jerry

Look at this photo of my 73, 23...

http://www.gmcmhphotos.com/photos/73-painted-desert-230/p19136.html

See the control valves in the lower right of photo? With the indicator on Travel, the ride height should adjust automatically. The other positions are intuitive Raise Lower and Hold. If you have some leaks you can set it to travel until it reaches normal height and then move to Hold -- sometimes that position leaks less.

The original valves are prone to issues and one solution is to replace with valves by JR. Slaten...

Look here

http://www.gmcmhphotos.com/photos/interior-remodel/p16807.html

Another solution is to add shrader vales at the airbags.

http://www.gmcmhphotos.com/photos/schrader-valve-for-air-bags/p35022-schrader-valve-ace-mike-k.html

But this requires you to manually add/release air to adjust height.

Does this help?

Dennis

Dennis S
73 Painted Desert 230
Memphis TN Metro

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Re: Rear End Low [message #278182 is a reply to message #278177]

Thu, 21 May 2015 22:47

A Hamilto

Messages: 4508
Registered: April 2011

Karma: 39

Senior Member

To expand on all the other posts here, the rear rides on an air shock, usually called an air bag in this forum. First generation had a compressor mounted up front that filled a tank and there are height control valves in the wheel well to keep the rear at the correct ride height. Controls are on the dash for leveling at campsites. You can raise and lower each side independently of the other.

Now you can see there are lots of places for problems. Compressors get old and weak or die, leaks at connections, height control valves that raise but don't lower, lower but won't raise, dash control valves that leak, and so on. My 73 Sequoia will squat to the ground in about a day if set to "travel" mode, maybe three days in "hold". The CanyonLands has shut off valves and schraders and the passenger side will drop a few inches in three months, the driver's side won't seem to move in that time. The 73s (and 74s?) will break the wheel well if allowed to drop all the way, so put some blocks under the bogeys to keep that from happening if you are going to be away from it longer than it can stay up.

Listen for leaks, time how long it takes for the compressor to get from no air pressure to correct ride height, get the manuals for your year model and read how to set ride height. etc.

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Re: Rear End Low [message #278184 is a reply to message #278175]

Fri, 22 May 2015 05:25

GMC Cruse

Messages: 606
Registered: June 2009
Location: SE Michigan

Karma: 3

Senior Member

73 Canyon Lands 007 wrote on Thu, 21 May 2015 21:53

Thanks so much for all the excellent replies.

I have no manuals, so I am not sure if the air bag knobs on the dash are set properly.

Can someone point me in the right direction for them? And I will get the manuals.

Tks mucho grande.

Manuals:

http://www.bdub.net/manuals/

Mike K. '75 PB Southeast Michigan

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Re: Rear End Low [message #278185 is a reply to message #278184]

Fri, 22 May 2015 06:40

tphipps

Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL

Karma: 9

Senior Member

http://www.appliedgmc.com/prod.itml/icOid/690

These will allow you to refill the air bags from another compressor and allow you to isolate the air bags from a leaky system. Very simple installation.
I carry a small 12v (internal battery) compressor just for this purpose. It has enough capability to also inflate tires, a bit slowly, but better than nothing.

Tom, MS II

2012 Phoenix Cruiser model 2552 KA4CSG

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Re: Rear End Low [message #278206 is a reply to message #278175]

Fri, 22 May 2015 16:45

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

73 Canyon Lands 007 wrote on Thu, 21 May 2015 21:53

Thanks so much for all the excellent replies.

I have no manuals, so I am not sure if the air bag knobs on the dash are set properly.

Can someone point me in the right direction for them? And I will get the manuals.

Tks mucho grande.

I have a number of things for you.

First, welcome to the group, family, cult, asylum,

Second, you seem to have an immediate need for a native guide. If fact you maybe should have engaged one long before this. If you tell people where you are can probably get one quickly. On the page where you found the manuals there is a Black List aka GMC assist list. Get that and read it.

Third, we go by real names here most of the time. This simplifies things greatly when you meet another owner, and you will. When you have been exchanging remarks online, and you meet and he acts like he has no idea who you are that is because he has NO Idea who you are.

Forth, your coach should have two round knobs to the driver's right. When not moving, set those to "Hold". When you put the coach in drive, a light and buzzer will remind you to set those to "Travel". Do it.

Fifth, if you notice, most everybody here has a sigfile (signature lines) that say: Who is writing, a short about the coach and any specific mods that might matter and finally a geographic reference so if someone that might choose to assist you will know if he is in striking range. Can you see how all of this can help?? (73 canyon lands was a very popular coach)

Lastly, now that you have found your way here, you are a member of a community like few others. There is a vast collection of experience here an it is well worth your while to take advantage of it. This board can be searched effectively and that will always be a good start. But, ask question too. As you did. Because this community so reminds me of the watermen that are my world, I have taken to welcoming new owners much as a new owner or vessel would be welcomed there. So,

May the Good Lord bless this coach and all those that set forth withing her.
Welcome Jerry

(You can change the alias that gets displayed in Control Panel/Account Settings then scroll down to update. This is also where you can put in a sigfile (under Preferences).

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: Rear End Low [message #278218 is a reply to message #278206]

Fri, 22 May 2015 21:12

Neil

Messages: 271
Registered: July 2007
Location: Los Angeles and Magalia, ...

Karma: 1

Senior Member

Dear 007

I am in LA, but it is a big place. Where are you. I have had a 76 cash eating beast for about 12 years and might have some insights for you.

Feel free to PM me.

Neil
76 Eleganza now sold
Los Angeles

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Re: [GMCnet] Rear End Low [message #278222 is a reply to message #278175]

Sat, 23 May 2015 04:00

Bruce Hart

Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming

Karma: 5

Senior Member

You can look this tech write up by Duane Simmons.

http://gmcws.org/Tech/dsimmons/air_suspension/air-suspension-system.html

Reference drawing for the different colored tubing.

http://www.gmcmhphotos.com/photos/air-bag-system/p44538-power-one-air-connections.html

I keep an excel file for a reference to all the tid bits that comes across
the forum here and other information that I dig up on the coach. I keep
separate pages for different areas of the coach like engine, transmission,
heating and cooling, suspension, etc.

On Thu, May 21, 2015 at 7:53 PM, Jerry wrote:

> Thanks so much for all the excellent replies.
>
> I have no manuals, so I am not sure if the air bag knobs on the dash are
> set properly.
>
> Can someone point me in the right direction for them? And I will get the
> manuals.
>
> Tks mucho grande.
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>

--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart 1976 Palm Beach 1977 28' Kingsley La Grange, Wyoming

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