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Old 12-21-2009, 04:43 AM   #1
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Question Rear air bag replacement and system mods

The Air bags for the rear are Firestone part # WO 1-358-5412 these are the correct replacement for the 345 ( I have seen others listed but they have a lower piston height which is different from standard and would allow it to go too low), they have the added advantage of a built in bump stop in side so it should stop the coach leaf springs from making contact with the main frame if the airbags fail
( mine clearly has damage is minimal but not ideal ) I got these ordered from 'truckspring.com' @ $140 each which I thought was a good price.
I am modifiying the system so the air bags are independent of each other and can be controlled by individual pnumatic switches with two dual gauges. the fronts can be set to 55 ibs and left there, the backs will be set at 10 1/2 inches ride height, on level ground, then using a Teleflex Telvaor indicator sytem ( used on boats fro trim tab position) adapted I can calibrate this to know form the driving seat the exact height at all times ( doing away with the compesating valve system). Also adding a seperate gauge for the tank. This way I have full controll of the system and I am also going to incorporate a manual air switch over from the compressor and tank that I am using for the air horns, so I get another back up ! sounds a bit over the top but while I'm down there it gives me a fall back as well as air valves.

many more upgrades including Intellipower 80A to replace the Univolt, Inside coach LED lighting, dual solar panels 60W each, one for each battery system, Supersteer bell cranks and arms.

Wish list is a Duramax + Allison 6 speed

all I need is a littel time . . .
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Old 12-21-2009, 04:59 PM   #2
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Originally Posted by moonshine View Post
I am modifiying the system so the air bags are independent of each other and can be controlled by individual pnumatic switches with two dual gauges. the fronts can be set to 55 ibs and left there, the backs will be set at 10 1/2 inches ride height, on level ground, then using a Teleflex Telvaor indicator sytem ( used on boats fro trim tab position) adapted I can calibrate this to know form the driving seat the exact height at all times ( doing away with the compesating valve system). Also adding a seperate gauge for the tank. This way I have full controll of the system and I am also going to incorporate a manual air switch over from the compressor and tank that I am using for the air horns, so I get another back up ! sounds a bit over the top but while I'm down there it gives me a fall back as well as air valves.
moonshine,

I for one would like more information on what you're doing and how you're doing it. Our 310 only has one leveling valve and I would really like to switch it over to two valves/switches.

Quote:
Wish list is a Duramax + Allison 6 speed

all I need is a little time . . .
Heck, all I need is a little time AND money....

Brad
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Old 12-22-2009, 03:19 AM   #3
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Hey Brad,

ok basically I have started again with the air lines so I am still using the exsisting compressor and air tank, I have added a quad air control panel (Firestone #2333) this has two gauges, each with two needles, so one gauge for the front and one for the rear, the two needles will do left and right air bags. the panel has four pneumatic switches, that mean you can manually control each air bag. the fronts should run at 55 psi all the time ( factory recommended) and the rears should be at 10 1/2 inches from the top of the air bag to the bottom. The original levelling switches where attached to the tag axle so stopping to much weight being put on the tag axle. So my intention is to fit a Teleflex televator trim tab position indicator to replace them and make adjustments manually. These position indicators are simply two 75 ohm potentiometers fixed to the tag on either side and two coresponding gauges ( bit like a fuel gauge on it side) showing up and down measurement. I will have to calibrate this system so the gauges read correctly. this can be achieved by adjusting the length of the connecting arm to the potentiometer to vary the movement so I can get the midway mark on the gauge to be the correct ride height and know how much the upper and lower marks are indicating in relation to the tag axle movement. I would set this up be having the gauges provisionally hot wired under the vehicle so I can see the results of my adjustments. The air line are simple, they run from the compressor via a non return valve to the tank and from the tank to the panel, from the panel four individual lines then run to each air bag. the compressor will be controlled as before by the electrical pressure switch that will turn it on for low pressure in the tank and off when it reaches its high pressure setting. I was going to add a gauge to that part of the system to know the tank pressure, but that is a little extra that isnt really needed to make the system work.

Alternativly you can buy the OEM levelling switches that Airstream fitted from Firestone. I found my gauges and front bags at Summit Racing ( write firestone in the search window and then choose suspension components ) the OEM switches are there, the panel is under electronic control although its pneumatic. I got my rear airbags and fittings from Truckspring.com ( Michigan Truck ).

well good luck and if I can help anymore let me know by sendind me a message to my private messages inbox and it will email me to let me know that I have mail on the forum !

kindest regards, Paul.
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Old 12-22-2009, 07:20 PM   #4
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When I adjusted my height to 10 1/2 inches, the tag was off the ground. I ended up setting the height at the minimum. That was 1 1/2 inches higher then it was. I think I only had 3/4 inch between the frame and the spring end before. I was working on building a platform on the axle for the rubber bumpers when I read the book about the bag measurement. If I recall the book says it's set at the factory by the weight on the tag. I have yet to find a scale that's even and level on the ends to get the weight on the tag.
That's been years ago. I haven't replaced any front-end part sense. Before it was $600+ every year on the front-end.
mel
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Old 12-23-2009, 08:02 AM   #5
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1989 34.5' Airstream 345
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I find all of this very helpful and interesting. Thank You for the updates and research that you have provided.
the week before Thanksgiving I took our 345 into Columbus, Spring, frame and Brake. I ask them to go through the undercarriage front and back and to align the front end. They gave the 345 a clean bill of health. And the bill was $125.00
With only 50 thousand on the chases, sitting even at all 4 corners on level ground and after a close inspection myself this summer I see no issues concerning anything but Like new condition.
I am also open to any and all methods of making improvements.

I have been working, experimenting on the tire pressure and right now this is what I am running

Front 74
drive 84
tag 74

As I find after reading, and the above post's verify ! that there may be to much pressure on the tag axle for what it is designed to carry and causing failure of bearings and races, Hubs
So the idea of a separate air bag pressure adjustment is needed for the drive and tag axles
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Old 12-29-2009, 09:24 PM   #6
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Moonshine & Co!

I am restoring 84 AS and have just made it to the rear axle. There is no book on the system and I haven't a clue if it is working properly. I know the compressor kicks in every time when I turn on the ignition, but I see no gauge to indicate PSI or proper level. Would appreciate some "air bag for dummies" info.

PD
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Old 12-29-2009, 10:11 PM   #7
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hello pdallas, well, I can not help much ! But the 1st. thing to do is crawl under and lay there scoping out the system.

1. are the bags all inflated ? that is a start !

2. loosen the drain valve under the air tank , this should be done every 3 to 6 months so no moisture accumulates in the system !

3. Trace all of the air lines from the tank and see where they go so you get an idea of how the system is tied together.

After a fer hours of inspection, light service you will have a much better visual idea of how your system works. If your bags hold air, look good, no cracks ? Bulges ? then you can set the Coach on level ground and Measure all 4 corners and see how even you set.

John

Happy New Years Every one
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Old 12-29-2009, 10:19 PM   #8
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Moonshine & Co!

I am restoring 84 AS and have just made it to the rear axle. There is no book on the system and I haven't a clue if it is working properly. I know the compressor kicks in every time when I turn on the ignition, but I see no gauge to indicate PSI or proper level. Would appreciate some "air bag for dummies" info.

PD
There is a very small brass check valve, that is in the output side of the air compressor.

If for any reason, the check valve fails, the air bag pressure will bleed off back thru the compressor, slowly, but surely.

If the rear end sags after setting for a few hours, then if the rear bags are OK, the "check valve" becomes the bleed down problem.

The original check valves were very small at about 1/2 inches wide and about 1 1/2 inches long.

Andy
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Old 12-29-2009, 11:42 PM   #9
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Hello Andy, If the check valve does need replacing ??? what do you recommend ?

Thank You

John
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Old 12-30-2009, 03:16 AM   #10
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Hello Andy, If the check valve does need replacing ??? what do you recommend ?

Thank You

John
That check valve, is an Airstream available part.

I will post their part number later today, when I am at my office.

Andy
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Old 12-30-2009, 03:44 AM   #11
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Hello John Haggard and pdallas if you go up one level back into classic mo section then look below in the list there is a post ' Electrical Schematic 1985 325 MH ' by Kingoreilly, 2nd post on it from Bkahler known as Brad has put a PDF document link, if you download this everything you could possible need is on it ! ( well done Brad ! )

Regards, Paul.
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Old 01-03-2010, 09:45 PM   #12
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Gentlemen:

Thanks for the excellent advice.

PD
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Old 01-04-2010, 02:29 PM   #13
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Hello John Haggard and pdallas if you go up one level back into classic mo section then look below in the list there is a post ' Electrical Schematic 1985 325 MH ' by Kingoreilly, 2nd post on it from Bkahler known as Brad has put a PDF document link, if you download this everything you could possible need is on it ! ( well done Brad ! )

Regards, Paul.
Paul,

The Airstream part number for that air line check valve is, 601232.

Be prepared, they are not cheap.

Sorry for the delay in getting back to you.

Andy
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Old 01-05-2010, 10:34 AM   #14
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Andy, I think that last post is for John Haggard
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