Adding a dump valve on spread axle

you said the bags are all tied together, you will need a one way valve to separate the front from the back

 

Search for skateboardman posts. He added one and tells you how.

 

A one-way, or check, valve won't do the job. You need to isolate the rear bags from the front when you dump the air. A one-way valve just prevents air from travelling against the flow direction (reverse of normal flow). Such a valve would also upset the balance between the front and rear bags as it would prevent air from being dumped from the rear bags during normal operation.

 

If the lines going to the rear bags are tied in with the front ones then you will need a valve for each side.
I have two trailers that have dual leveling valves & this was how they had to be hooked up to work,one of these had the valve to dump when parked.

 

Hey Kwswan, was that you I chatted to going thru the guitar on 440 last year?

free2fly get rid of that auto dump valve. set it up right.

How to plumb air bags:

Air should come from tank to pressure protection valve to manual 3-way ball valve (to dump all four) then to height control valve to electric 3-way valve (for dumping rear only).

On electric 3-way valve one port goes to front bags, one to rear bags and other to atmosphere.

Here's link to good electric dump valve that I use. http://peterpaul.com/valves/3-way-directional-control/1752-2/

P/N for manual dump 3-way ball valve is Hendrickson number AK-147-1 but other trailer mfrs have this same valve under different numbers. I have a hard time finding anyone who carries it any more. They'd rather sell you a push-pull type with o-rings.

Auto dump is not good, you should dump air first, then when bags are empty is when you set brakes. This avoids force against bushings and brake shoes when brakes are applied before trailer has a chance to lower.

 

Yep that was me.