Bed Lowering Mode with Auto-Level Rear Air Suspension

[Saskman]

New 2024, 3500 MC SRW Limited Edition with Bed Lowering.

I'm assuming that for the "Bed Lowering" to work properly the air bags for the "Auto-Level Rear Suspension" should have some air in them when the the truck is empty and in normal ride ride height? Otherwise how would the truck be able to lower the bed.
The problem that I'm having is the air bags are not inflated in normal ride ride height, therefore when activating the bed lowering nothing is changing....

I've been searching through this site through different forums and with UNCLE GOOGLE and cannot find any answers:
- Should the air bags have some air in them at normal ride height?
- If the air bags were to be inflated to allow for bed lowering would that change the ride of the truck? Would be be less bucky?
- I know that it not a an SUV with independent rear suspension and I can live with ride as is but I would like to be able to have the bed lowering available to help in hitching up to trailers etc.
- I measured the height from ground to rear wheel wells, on a level shop floor surface, and in normal and bed lowering modes the measurement is the same. Both side are even at 41 1/4".

Am I missing something????

Before I stop by the dealership i would like to have a better understanding of the Bed Lowering and how its supposed to function.

Thanks

 

[CdnHO]

The bed will only lower with significant weight in the bed since the leaf springs support the rear end when empty. If you want a reasonable ride when empty weigh the truck and use the tire load/inflation tables to determine tire psi. I use the door sticker values when load and 64 front and 35 rear on my dually after consulting the appropriate load/inflation table. Rides pretty nice empty that way.

 

[AH64ID]

Go look at your rear springs and see if the main leaves are resting on the bumpers for the lower overloads in normal ride height, it sounds like they are.

There should be around a 1/2"-3/4" gap, and when you go to bed lowering mode the truck will lower onto the overloads. That's all the lower you will go empty, but if you have some payload on the rear springs you could go lower.

If you're resting on the lower overloads you can adjust your ride height sensors and get the truck to sit a little higher. This will likely improve the ride as well.

You should lower ~1" when you go into ALT ride height, and you it usually takes 500-750lbs in the bed to engage ALT.

Bed lowering doesn't drop much empty, so I rarely use it, but it's come in handy a few times.

 

[Saskman]

Sorry for the delayed response, I'm hopping to be able to take a closer at the system this afternoon and try a few things as suggested by AH64ID. I will air down the tires from 70 Psi to 55Psi and see what happens as per CdnHO, then i will play with ride height and adjust the air leveling sensors slightly to have a little more air in the bags.
Once I adjust and try different settings I will get back to to the forum with results.

Thanks all for the time to help.

 

[AH64ID]

55 psi is good for the front, if you’re empty take the rears to 35 psi. That’s still enough air for a rear axle weight of just over 4,000lbs.

 

[Saskman]

After airing down the rear tires to 50 Psi and taking it for drive, I opted out for time been on adjusting the auto level sensors, I think that the driver side air bag was more inflated do to the fact that i had full tank of fuel. I will check the air bags when it closer to empty just to see if that is why the driver side was harder.
The measured distance from grade to wheel well is relatively close so it, in my mind, makes sense that driver side would have be firmer. It need to compensate for the extra 250Lbs of fuel.

The Ride has improved immensely, I'll know for sure when the "Warden" gets in for ride and see if she notices.

I'll keep the forum informed.

Thanks All

 

[AH64ID]

You really need to look at your springs and see how much of a gap is in between the main leaves and the overloads.

 

[desertskier]

Bed lowering mode doesn't change the rear height of my truck unless there is a load. The display says it works and I hear noises coming from the system but the amount of air in the bags doesn't seem to change and the overloads are not touching the main springs. With a load it drops the rear 3/4 to 1". When my truck was new the drivers side bag had air in it all the time whether the fuel tank was empty or full as do many others on this forum. I adjusted the arms to run with both bags empty. With both bags empty the overloads are not touching but they would bang when I hit large bumps so I recently adjusted them to raise the rear slightly to eliminate the banging. It rides about the same with no air vs. a small amount of air but the overloads don't hit over bumps.

 

[AH64ID]

Bed lowering mode doesn't change the rear height of my truck unless there is a load. The display says it works and I hear noises coming from the system but the amount of air in the bags doesn't seem to change and the overloads are not touching the main springs. With a load it drops the rear 3/4 to 1". When my truck was new the drivers side bag had air in it all the time whether the fuel tank was empty or full as do many others on this forum. I adjusted the arms to run with both bags empty. With both bags empty the overloads are not touching but they would bang when I hit large bumps so I recently adjusted them to raise the rear slightly to eliminate the banging. It rides about the same with no air vs. a small amount of air but the overloads don't hit over bumps.

Since you’re not riding on the overloads in normal bed lowering mode should work empty as it empties the bags and that will drop you onto the overloads.

 

[desertskier]

I agree but it doesn't. The bags don't empty. Also, when the bags are adjusted to be empty my overloads do not touch. There is about 1/4 to 1/2" gap. Since my truck is one of the ones that had air in the drivers side but not in the passenger side when it came from the factory I assume that there is something wrong with the system. I think it's a calibration problem but I really don't know. The system seems to work with a load so I don't really worry about it.

 

[AH64ID]

I agree but it doesn't. The bags don't empty. Also, when the bags are adjusted to be empty my overloads do not touch. There is about 1/4 to 1/2" gap. Since my truck is one of the ones that had air in the drivers side but not in the passenger side when it came from the factory I assume that there is something wrong with the system. I think it's a calibration problem but I really don't know. The system seems to work with a load so I don't really worry about it.

There is a minimum pressure for the bags, so adjusting the sensors shouldn’t empty them. To empty them the truck needs to be in bed lowering mode or transport mode.

 

[desertskier]

I just tried bed lowering mode and transport mode without a load. The passenger side feels like it is close to empty but the drivers side still has air and is pretty firm. I think it goes back to the original problem that the system thinks the drivers side is at minimum pressure but it isn't. Based on the posts I've read I think there are a lot of trucks that have this problem. Do you know if anyone with this problem has had a dealer look at it and if they corrected it? I've only seen the posts that mention the problem but I haven't seen a resolution other that adjusting the arms so the bags are even.

 

[AH64ID]

I haven’t heard of anyone taking it to the dealership, but it’s worth a shot.

 

[gimmie11s]

I just tried bed lowering mode and transport mode without a load. The passenger side feels like it is close to empty but the drivers side still has air and is pretty firm. I think it goes back to the original problem that the system thinks the drivers side is at minimum pressure but it isn't. Based on the posts I've read I think there are a lot of trucks that have this problem. Do you know if anyone with this problem has had a dealer look at it and if they corrected it? I've only seen the posts that mention the problem but I haven't seen a resolution other that adjusting the arms so the bags are even.

Adjust the sensor on the driver's side. There is enough room in the factory hole/mount to adjust the sensor 1/8" or so. That may be enough to equal out the air in each side a bit.

 

[desertskier]

I have adjustable sensor rods. They are adjusted to keep the bags with an equal amount of air for normal ride height but that doesn't solve the bed lowering issue. The system should empty both bags but it doesn't.

 

[gimmie11s]

I have adjustable sensor rods. They are adjusted to keep the bags with an equal amount of air for normal ride height but that doesn't solve the bed lowering issue. The system should empty both bags but it doesn't.

Then one of your rods is adjusted wrong.

I have the same rods and can get both bags to empty out. No, I don't have them both adjusted equally.

 

[desertskier]

Then one of your rods is adjusted wrong.

I have the same rods and can get both bags to empty out. No, I don't have them both adjusted equally.

Just to be clear. I can adjust the rods so that both bags are at minimum pressure (empty) and ran like that for about a year. Recently I adjusted them to add some air so that the main springs don't bang into the overloads when I hit large bumps. So both bags are currently running about the same amount of air in normal ride height to raise the rear slightly. In order to achieve this the rods are not adjusted to the same length. If I command either bed lowering mode or transport mode the passenger side empties but the driver side does not. It would make sense that both bags should empty to lower the bed but they don't. Do you have them adjusted for minimum pressure for normal ride height? What happens with bed lowering mode with no load?

 

[gimmie11s]

Just to be clear. I can adjust the rods so that both bags are at minimum pressure (empty) and ran like that for about a year. Recently I adjusted them to add some air so that the main springs don't bang into the overloads when I hit large bumps. So both bags are currently running about the same amount of air in normal ride height to raise the rear slightly. In order to achieve this the rods are not adjusted to the same length. If I command either bed lowering mode or transport mode the passenger side empties but the driver side does not. It would make sense that both bags should empty to lower the bed but they don't. Do you have them adjusted for minimum pressure for normal ride height? What happens with bed lowering mode with no load?

Yeah, that makes more sense and sounds similar to how ive messed around with mine. My truck is DRW so I have mine adjusted to keep almost no air in the bags unloaded. Once I hook up our 5er or throw some weigh in the bed though, the truck adjusts and air is added right away.

I will say... if I go a few weeks without checking, ill do a random air bag check and one of them is firmer than the other. What I do is "reset" them by hitting the bed lowering button so they air out completely, then let them air back up to reset. Some times it takes it a couple tries to even everything out.

 

[Saskman]

Go look at your rear springs and see if the main leaves are resting on the bumpers for the lower overloads in normal ride height, it sounds like they are.

There should be around a 1/2"-3/4" gap, and when you go to bed lowering mode the truck will lower onto the overloads. That's all the lower you will go empty, but if you have some payload on the rear springs you could go lower.

If you're resting on the lower overloads you can adjust your ride height sensors and get the truck to sit a little higher. This will likely improve the ride as well.

You should lower ~1" when you go into ALT ride height, and you it usually takes 500-750lbs in the bed to engage ALT.

Bed lowering doesn't drop much empty, so I rarely use it, but it's come in handy a few times.

Finally today I had a chance to look at the issue closer.
To begin with I lowered the truck using bed lowering and the height when all air was out of the air bags, both were evenly soft, the wheel well to ground measured 44”.
I then adjusted both ride height sensors to allow more height when aired up to normal ride height and now I’m gaining 3/4”. The original ride height today after reducing the tire pressure the other day was just short of 44 1/4”.
As for the overload bump stops the back of each was just resting on leaf spring and the front I could just get my pinky finger in the space (1/2”).
After all the adjustments to the ride height sensors the overloads back bump stops are 1/2” to 3/4” and the front about 1” of space.

I live in country and due to the 2” of rain yesterday and the spring thaw the roads are mess so I’m hoping to be able to get in on the highway in the day or so and see how it rides.
Now if I switch on Alt Ride height the bed lowers about an 3/4” when empty, the same when activated bed lowering. I’m assuming it’s going as low it can.

So far I’m happy with results. Just for sh__s and giggles I installed the Rhino Hitch receiver and measured the drop with bed lowering and I can drop 5/8”.

Thanks to all of the members for the advice and support.

 

[Brutal_HO]

If you can run Alt height unloaded, you have enough actual (or sensed) weight to allow it. My SRW with a crossover box full of stuff and hitch installed won't go into Alt Height unless I hook up the 5th wheel or boat.