'21 3500 Rear Air Suspension - Smoooth Ride!

[heavyg603]

Thought I'd give an update to my original findings. I'll once again preface by saying that these are my findings only. I'm all ears if someone is able to provide additional information on how this system operates. I'd also be grateful if anyone is able to provide the section describing Rear Air Suspension from the RAM Shop Manual.

I'm very satisfied with how my truck (see sig) rides both empty and loaded. Loaded in my case is a Grand design 2930RL S-Class Solitude with approx 2500 lbs pin weight. While some may say 'its a 3500 and is supposed to ride stiff - get over it' my reply is that its also my daily driver and I know that with some work these trucks can be made to ride better.

My definition of a smooth unloaded ride? Prior to any of the things I did, I noticed that the rear was much stiffer than the front. When going over a bump the front would be fairly smooth while the rear would jolt my behind. After the adjustments etc, my rear suspension now feels just like the front. While it will never ride like a half ton, the sharpness of the ride is much more reduced.

Since I last wrote in this thread, we've towed the 5th wheel approx 500 miles which has allowed the rear suspension to settle. While my drivers side bag was still soft, it was not as supple as the passenger bag was. My assumption all along has been to have the bags empty when the truck is empty with full fuel. In my case the drivers bag has always been more firm than the passenger bag. To get the drivers side height sensor to let more air out of the bag, I needed to elongate one of the mounting holes. I used a dremel to remove a small amount of material as shown in the photo. After doing this, the drivers bag is now as supple as the passenger bag. Note that I've never anything to the passenger side of the suspension - my goal all along has been to get the drivers side the same as passenger via adjustment of the height sensor.

In summary, my combination for a very acceptable ride empty is the following:

1. Height sensors adjusted so that both bags are supple when truck is empty and fuel full.
2. Rear tire pressure is 42 lbs or less - note that I have the 20 inch wheels on mine. Either way, take advantage of the load range charts. There is no reason to keep the rears at 80 lbs! Front air pressure is 60 lbs.
3. Keep a full fuel tank - this seems to give the best ride.

So in order to achieve the softer ride the idea was to make sure the bags are both soft at empty? So essentially you are on the springs only?


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[roegs]

So in order to achieve the softer ride the idea was to make sure the bags are both soft at empty? So essentially you are on the springs only?


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Exactly....I went on the premise that with fuel tank full and truck empty both bags should be soft. It did not take much movement on the height sensors to get both bags soft. I think I read that RAM shop manuals can be rented for a couple days (vs high dollars to purchase) so I may do that one of these days so I can read the air suspension section. For now I'm happy. Just hauled our 5th wheel 1300 miles and the rear suspension leveled very nice with the weight of the pin (around 2500 lbs).

 

[Myilarion]

This is great to know ! my 2020 ram 3500 is as you described with one air bag being firm and one feeling empty ? I thought they were tied together like my gmc 2500 duramax but obviously they are not . I have a 2021 on order so probably wont bother messing with this one but thanks for your insight so i can check the new one after it finally gets delivered ( If it ever does anyway since its been stuck at the body vendor since the 3rd of march with no updates ! )

Great article, I have the same rough ride on my 2019 ram 3500 DRW with the heavy tow package. My airbags were the same as yours. I think the driver's side air bag is pumped higher to compensate for the extra weight of the fuel tank. at almost 7lbs per gallon depending on the density which can be 6.2 to over 7lbs per gallon depending on OAT. Thats 252 to 364 extra lbs. on drivers side with full fuel depending which size tank you have.

 

[roegs]

Great article, I have the same rough ride on my 2019 ram 3500 DRW with the heavy tow package. My airbags were the same as yours. I think the driver's side air bag is pumped higher to compensate for the extra weight of the fuel tank. at almost 7lbs per gallon depending on the density which can be 6.2 to over 7lbs per gallon depending on OAT. Thats 252 to 364 extra lbs. on drivers side with full fuel depending which size tank you have.

Interesting thought about the drivers side bag being pumped more to compensate for fuel weight. If that was the case, I'd think that with an empty (or near empty) tank the drivers side bag would feel the same as the passenger bag. Have you tried that?

 

[desertskier]

This video has some good information related to this. The idea of calibrating the sensors seems reasonable. You would think that with the sensor output voltages being equal the system would put the same amount of air in each of the bags (assuming equal or no voltage loss from the sensor to the controller). The end result he was looking to achieve is different than what roegs wanted but he started with the same issue.

 

[roegs]

This video has some good information related to this. The idea of calibrating the sensors seems reasonable. You would think that with the sensor output voltages being equal the system would put the same amount of air in each of the bags (assuming equal or no voltage loss from the sensor to the controller). The end result he was looking to achieve is different than what roegs wanted but he started with the same issue.

This is a great video....thanks for posting! As desertskier mentioned, the author of the video was trying to achieve a different result than I was. My desired state was having both rear bags empty so that the truck would ride only on the rear spring packs (empty truck bed). The author of the video believed there would be a better ride with the bags slightly filled. He was looking for approximately a 1 inch lift when the truck was empty. Couple thoughts:

1. I liked the idea of measuring voltage on the sensors. I measured both of mine. Drivers was approx 2.9 volts and passenger was approx 2.4 volts. Both of my bags are deflated. There is no change my suspension when I go to 'bed lowering' mode. Truck height remains the same as does sensor voltage. This somewhat confirms that the bags on my truck are basically empty.
2. There are two schools of thought on the best ride quality (unloaded) when adding air bags to a rear leaf spring suspension. One is that the bags should be slightly filled so that the first inch or so of suspension travel is riding on the air bags. Second is that the bags should be basically empty. I would love to talk with a RAM suspension engineer to hear what their desired state is for our trucks when the bed is empty.
3. This video and other discussions about RAM 3500 rear air suspension ride quality confirms once again that there is inconsistency in air bag settings when these trucks leave the factory. JB Reviews on YouTube just tested 2 RAM 3500 dually's. One had standard suspension and the other had air. JB praised the air suspension for ride quality, but in the comments section there was (once again) praise from some while others wish they'd have never ordered the air option.
4. One thing remains the same - lowering rear tire air pressure when empty definitely helps. When not towing our 5th wheel, my 3500 is basically a grocery getter. I air down to 40 lbs and enjoy a very respectable ride with even tire wear.

Thanks to all who have contributed to this thread. It's been a learning experience for me and I hope to learn more about the in's and out's of this suspension.

Scott

 

[John Jensen]

This is a great video....thanks for posting! As desertskier mentioned, the author of the video was trying to achieve a different result than I was. My desired state was having both rear bags empty so that the truck would ride only on the rear spring packs (empty truck bed). The author of the video believed there would be a better ride with the bags slightly filled. He was looking for approximately a 1 inch lift when the truck was empty. Couple thoughts:

1. I liked the idea of measuring voltage on the sensors. I measured both of mine. Drivers was approx 2.9 volts and passenger was approx 2.4 volts. Both of my bags are deflated. There is no change my suspension when I go to 'bed lowering' mode. Truck height remains the same as does sensor voltage. This somewhat confirms that the bags on my truck are basically empty.
2. There are two schools of thought on the best ride quality (unloaded) when adding air bags to a rear leaf spring suspension. One is that the bags should be slightly filled so that the first inch or so of suspension travel is riding on the air bags. Second is that the bags should be totally empty. I would love to talk with a RAM suspension engineer to hear what their desired state is for our trucks when the bed is empty.
3. This video and other discussions about RAM 3500 rear air suspension ride quality confirms once again that there is inconsistency in air bag settings when these trucks leave the factory. JB Reviews on YouTube just tested 2 RAM 3500 dually's. One had standard suspension and the other had air. JB praised the air suspension for ride quality, but in the comments section there was (once again) praise from some while others wish they'd have never ordered the air option.
4. One thing remains the same - lowering rear tire air pressure when empty definitely helps. When not towing our 5th wheel, my 3500 is basically a grocery getter. I air down to 40 lbs and enjoy a very respectable ride quality with even tire wear.

Thanks to all who have contributed to this thread. It's been a learning experience for me and I hope to learn more about the in's and out's of this suspension.

Scott

Scott,
One comment about running with empty airbags. All of the aftermarket airbag instructions say to run with at least 5psi to preclude airbag damage. Some, like my Timber Groves will not air down below 5psi

 

[roegs]

Scott,
One comment about running with empty airbags. All of the aftermarket airbag instructions say to run with at least 5psi to preclude airbag damage. Some, like my Timber Groves will not air down below 5psi

Thanks John....thats a very good point. I did an edit to my comments above and removed where I said 'totally empty'. Although I have my RAM bags as low as I can get them, your comment probably holds true for this system also - there most likely is a small amount of air in them.

 

[Brutal_HO]

Scott,
One comment about running with empty airbags. All of the aftermarket airbag instructions say to run with at least 5psi to preclude airbag damage. Some, like my Timber Groves will not air down below 5psi

Not all. Airlift without the internal jounce bumper recommends 5psi minimum. The models with the internal jounce bumper can be run empty/wide open. They do that to prevent damage to the bag if compressed too much without air in them. If you ran bags at 0psi, basically atmosphere, when they compress there would be pressure.

I think what the guy in the video point is, somewhat like Timbrens, "empty" bags are compressing and then offering resistance. So it's like bumping off bump stops, overloads, etc. For an unloaded truck, that can be an unsettling/bumpy ride.

 

[desertskier]

When I first read this thread I checked my air bags and the driver side had some air but the passenger side was empty. We were about to drive across country without a load and I wanted the softest ride possible. So I loosened the sensor bolts on the driver side and adjusted it so that the bag was empty. Since then I noticed that the system was activating/making noise at various times with the engine off. It would activate when I approached the truck or opened a door or the tailgate. I decided this probably isn't correct so I was going to set the sensor location back to the factory location when I found this video. I measured the voltages and there was about 0.5V delta between the two. My guess is that the system needs to see the two voltage inputs within a certain tolerance of each other or it thinks there is a problem. For the time being I set the bracket location back to the stock position just to see if the system stops activating randomly. It appears to have stopped and it is back to having the driver side bag with some air. The voltage outputs in the stock/parallel to the frame position result in about 2.4 - 2.5 volts from each sensor. Next I'm going to make some adjustable rods and make small changes to try and equal out the bags. I'm still curious why only one bag has air with both voltages being pretty much equal. I might try and read the voltages at the controller input just see if they are the same as at the sensor output.

 

[Xflight29]

I find if you once in a while, while not with any load, just activate the system and it wakes it up and evens out air-bags.

 

[CdnHO]

When I first read this thread I checked my air bags and the driver side had some air but the passenger side was empty. We were about to drive across country without a load and I wanted the softest ride possible. So I loosened the sensor bolts on the driver side and adjusted it so that the bag was empty. Since then I noticed that the system was activating/making noise at various times with the engine off. It would activate when I approached the truck or opened a door or the tailgate. I decided this probably isn't correct so I was going to set the sensor location back to the factory location when I found this video. I measured the voltages and there was about 0.5V delta between the two. My guess is that the system needs to see the two voltage inputs within a certain tolerance of each other or it thinks there is a problem. For the time being I set the bracket location back to the stock position just to see if the system stops activating randomly. It appears to have stopped and it is back to having the driver side bag with some air. The voltage outputs in the stock/parallel to the frame position result in about 2.4 - 2.5 volts from each sensor. Next I'm going to make some adjustable rods and make small changes to try and equal out the bags. I'm still curious why only one bag has air with both voltages being pretty much equal. I might try and read the voltages at the controller input just see if they are the same as at the sensor output.

I suspect the system wants to maintain the truck in a level attitude side to side. The left airbag probably has more air because it is heavier and more air pressure is needed to maintain the proper height. Perhaps due to fuel tank and other components on that side. I would think that if the truck is on a level surface both sensors would show the same voltage. The factory might even use that for calibrating the sensors. Not sure where one would find the documentation regarding the procedure for replacement of a sensor.

 

[gimmie11s]

I find if you once in a while, while not with any load, just activate the system and it wakes it up and evens out air-bags.

Ive found this to be true on mine as well.


The only way to tell the difference between non-air and an air truck is to ride in them/drive them back to back. This is what JB Reviews did. I have also done this. There is no comparison between non-air and air trucks. The air trucks noticeably ride better unloaded.

Remember the air trucks have a thinner leaf pack than the non-air so running your bags at or near empty will give a decent ride considering the truck is a 1 ton model.

 

[roegs]

....... This is what JB Reviews did. I have also done this. There is no comparison between non-air and air trucks. The air trucks noticeably ride better unloaded.

Remember the air trucks have a thinner leaf pack than the non-air so running your bags at or near empty will give a decent ride considering the truck is a 1 ton model.

This for me is the rub of the whole discussion. My experience is the same in that the air trucks will ride noticeably better only if the rear suspension is able to take advantage of the lighter spring pack. In my mind, that can only happen with bags at or near empty (as gimme11s stated above). Reading viewer comments on JD's video and comments on other forums on the air suspension, not everyone agree's that the air ride is better. I still believe it has something to do with system calibration at the factory.

Rainy day today so I had some time to go out and do some more playing with my truck...

1. A while back I had the chance to look at sections of a RAM Service Manual and glanced through the air suspension section. I believe it may have been a Gen 4 manual - anyway, the calibration process was complicated and involved various measurements that I believe were entered into their scan tools. Because of manufacturing tolerances, a given sensor voltage (say 2.5 volts) on both passenger and drivers side does not guarantee a level truck. I still believe that the best ride is obtained with both bags supple, which for me is being easily able to press inward on the bag with my thumb. Due to the way this system is calibrated, you could have each sensor at 2.5 volts and one bag could be firm while the other is supple.

2. I set my drivers side sensor back to where it was when my truck was delivered. I've never touched my passenger side sensor. The truck went right back to where it did when I originally started this thread - the drivers bag firmed up while the passenger bag remained soft. At that point, the drivers side height wheel well height was raised 1.25 inches higher that the passenger side. This became the truck's new normal. Even at that setting, there was only .15 volt difference between the two sensors.

3. Bed lowering mode.....while this does bring each bag at or near empty, the mode goes back to normal when the truck exceeds 5 mph. In this case it brought me back to drivers side being 1.25 inches higher due to the additional inflation of that bag.

4. Alt Height activation.....when pressing this button. the air compressor goes through its gyrations and eventually tells you that alternate height is not available. I believe it still goes through sensor measurements etc. but in the end it still returned me to the new normal of my drivers side being 1.25 inches higher due to the additional inflation of that bag.

5. Went back to my modified position of the drivers sensor and the system released the inflation of the drivers bag. Both bags are supple and the truck has slightly less than .5 different between drivers and passenger wheel well heights. I neglected to do a final voltage measurement between both sensors, but I believe its a couple tenth's of a volt. Again, I'm not sure that adjusting them both equal is the best way to ensure both bags are running at the lower pressure.

6. Compressor being chatty....I've experienced the same thing that desertskier mention about the air suspension system running even after the truck is off. There are times when I seem to just walk by the truck and the compressor will run and update pressures etc. Mine seems to do it both with the factory settings and the updated setting I did for the drivers side. I'll be interested to see what he experiences now.

Scott

 

[desertskier]

I still believe it has something to do with system calibration at the factory.

After making some measurements and putting the sensors back to the stock position I believe this is a factory calibration issue also, or lack of. I don't think there is any reason that the system would put a bias on the driver side to account for the fuel load or whatever. My truck sits higher on the drivers side with half a tank of fuel and no air in the bags so no reason to add air to that side. With the sensors in the stock position I have not heard any random system activations. I plan on leaving it alone for awhile to make sure I don't hear the chatty compressor and then adjust the driver sensor to remove the air by either by moving the sensor mount or using an adjustable sensor rod. My truck currently sits 3/4" higher on the driver side (using the Thuren height measurement method - wheel well lip to center of hub). Both sensor voltage outputs read ~2.47 +/- .02 at the sensors and the ASCM. Pretty annoying!

 

[desertskier]

Made some more adjustments and measurements (all voltage measurements made at the ASCM input). I waited a few days and did some driving between adjustments.

Started with both sensor brackets in the stock position: Driver side bag with air, Passenger side empty, no chatty compressor.

Turned driver side sensor bracket clockwise: Driver side 2.65V, both bags empty, compressor chatty.

Turned driver side sensor bracket counterclockwise slightly: Driver side 2.53V, both bags empty, compressor not chatty.

Thought that maybe ~2.5V is the magic number so adjusted the passenger side to 2.5V: Both bags where empty but compressor was chatty.

Moved the passenger side sensor bracket back the stock position: Passenger side 2.37V, Driver side 2.53V, both bags empty, compressor not chatty.

Ride height from wheel well lip to center of hub: Driver 25.25", Passenger 25.00".

When I say the compressor is chatty it was activating randomly with the ignition off. Mostly when I either opened or closed the driver door. Sometimes without me doing anything.

I guess this is where I am going to leave it unless something changes.

 

[roegs]

Desertskier....thanks for posting back. I have the same .25" difference between Driver and Passenger sides. When I first rotated my drivers side sensor clockwise I turned is as far as the mount allowed. This allowed me to hear the air escape from the drivers side bag. As time went on, I noticed times where the drivers bag did not seem deflated as much as the passenger so I used a dremel on the rear-most hole of the drivers sensor to allow just a tad more clockwise travel - I maybe removed 1/8" of material. Its interesting that you've gone between 2.53 volts and 2.65 volts on the drivers side and noticed differences with a chatty compressor. Thats not much movement (if I remember correctly!) of the sensor arm, and I'm wondering if differences in load (e.g. full vs half fuel tank, number of passengers, etc) may give that same delta in voltages. I notice my air system clicking / sensing many times when opening a door or lowering the tailgate. Please keep us posted on how your new setting work.

 

[C00P]

Not to parrot, but my bags were very similar to what some are describing from the factory, 1 hard and 1 soft. I did find when I let the air out of the bags to put in my 1” lift blocks and spacers that the passenger fitting was not properly seated in the regulator. I not saying that its the issue but these fittings are plastic and appear to be pretty easy to cross thread even from the factory. All I know is when I reconnected I spent the time to ensure the lines were connected properly and rebooted the compressor while checking with some soapy water. No leaks and both bags are now the same, so in my configuration with stock position and rods on the sensors they are now both soft.


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[jkacz123]

Has anyone dug into Alfa OBD or Jscan to do these adjustments? Wonder if it allow L/R adjustments on the 3500s? Have a 23 on order so just curious. On my 2018 grand I can adjust front vs back but not side to side.

 

[jkacz123]

The demo mode won't allow me last this point to see if it allows L/R adjustments. Anyone have Jscan?