Adding a second leveling valve

stupid question. is your frame tweaked? that could explain the lean. or i mihgt be so far off base its not funy

 

What kind of suspension do you have? Some are not very forgiving left to right and forcing it may make it run in a bind. If you have a typical leaf with the bag on the rear going to a bushing/eye on the front. You may just need different degree wedges on the saddles on 1 side. You need to make sure your pinion angles stay in spec when shimming.

I have seen the 2 leveling valve set up on an ambulance before, it was set up so the left and right were totally independent, which I only assumed was because of the amount of equipment on 1 side making it heavier on that side. I don't think that would be a good option for you since it'll only be compensating for the root cause and may cause other problems.

 

Air bag pressure is pretty slow to respond, You don't want it to fill fast over a bump, just to have to dump a lot of air after the bump. Generally front to rear uses a larger airline so the air can swap between the front/rear bags over bumps, but the air from side to side is either a small air line or has to go through the leveling valve because you don't want all the air swapping left to right around a turn. Separate left/right systems my be a benefit if you deal with a lot of long turns where air can slowly move from 1 side to another, but that's pretty rare. Most windy roads turn in both directions and have enough straights to equal out and these are the types of roads that your not going fast on.

What I would do first is jack the drives off the ground, use jack stands and shims to level the frame and allow the rears to hang. This should put the left and right spring eyes at the same level. Make sure the bags are deflated, the rear should be hanging on the shocks both sides the same. With the front of the springs level, the rears of the springs should also be level side to side. If they are shimmed differently left to right, the rear will not be level. If you measure from the frame (which has been leveled) to the rear of the spring at the same point left to right, those measurements should be very close. If they are not, the rear is not straight in the truck.

 

Let me input some real time information..

We had an issue with body roll and sway on the Dive Rescue trucks..the stock bags are connected in parallel, so as the body leans the air shift to the side with less weight ( not good)..
The solution was to connect the air bags separately via leveling valves so as to maintain the ride height.. What a difference in ride and control..

.... Philip

 

The HC valves don't react to every little change. They all have a neutral zone of so many degrees of travel.

But you might be on to something separating L&R sides.

Maybe tweak the cab bags too by fabbing some new brackets to make the mounting points wider and then separate them L&R too. I doubt as centered as the cab bags are stock that separating them would have any effect so widening them would be in order.

 

Let me be clear,, we split the chassis bags. The Rescue body sits on the frame..

Remember, when you lift a corner the opposite diagonal corner dives...In our case this was advantageous for Code 3 driving, helped pull the vehicle around the corners at elevated speed....

.... Philip

 

It should help. My old man ran a tri drive logging truck with the AG200 air ride which is notorious for body roll and he never had one complaint about it ever. Just make sure the leveling valves are the same p/n. I know one guy who put a different one on one side and it was extremely tippy.

 

If your problem was only body roll/stability, I may think that splitting the air bags would help you. What I'm more concerned about is that you said the truck leans. That is the issue I'd worry about first. Adding more pressure to 1 side to get you truck to sit level on level ground is a band aid for the real issue. No matter what you do to your leveling valve(s), you want the truck to sit straight with equal pressure in all the bags. This should be done by properly shimming the springs. Once the truck can support itself straight with equal weight on all the drives, then you can split the air bags to reduce body roll if you want.