2018 Silverado 3500 Rear Suspension

asilverblazer · November 4, 2025

I undertook some significant adjustments to the rear suspension of my truck, a 2018 Silverado 3500, 4x4 with diesel engine. This is on a 1 ton truck with the extra 2 leaf overload springs on top of the spring pack. The truck is a crew cab, standard (short) bed. It already was equipped with what I am reasonably certain to be a Loadlifter 5000 set of airbags, shocks are Bilstein 5100.

The bottom line is the truck rides too rough for my needs. Comparing the truck to all the others I've driven it is significantly more uncomfortable; mostly 1/2 ton trucks, but a few 3/4 ton and 1 ton trucks.

For reference the best ride and my target for comfort was my 2015 GMC Sierra, crew cab, short bed, 1/2

ton, 4x4, Z-71 with Bilstein 4600 shocks, Sulastic shackles, 20" BFG All-Terrain KO2's in factory size. This truck was exceptionally comfortable, comparable to some of my Cadillacs, albeit with too much motion while towing (I wish I put the 5100 shocks on).

This truck is only tolerable on the smoothest of roads, annoying on most and uncomfortable on rough.

There are two competing systems to make the ride more comfortable I need to remove spring rate and the only option without modifications is lowering air in the bags. This allows the truck to hit the air bag bump stops and is VERY harsh, to resolve this air has to be added to prevent bottoming out but the spring rate goes up and ends up harsh anyways so that there is no middle ground to be had that results in a comfortable ride. If you are loading 5000 lbs in the bed of the truck a compromise might exist; unladen it is impossible.

Prior to starting I typically ran with only 5 PSI in the bags, as a recommended minimum and to avoid increasing the effective spring rate unnecessarily. This still relied on the trucks springs which of course are rated very high and occasionally still bottomed out on the air bags.

I decided to try to lessen the spring rate more and use the air bags to make up the difference by removing some leaves from the spring pack. I removed the two bottom springs, the bottom one typically described as an overload and the one above it. This required removing the axle U-bolts and the bolt through the center of the spring pack. I ended up replacing this bolt with shorter ones (a regular grade 8 with the head rounded off to slip in the locating pin on the axle). I reused the U-bolts, there was just enough threads on them to take up the now shorter spring pack.

This effectively lowered the truck 1-2" (the thickness of the removed leaves) and exacerbated the bottoming out problem. With the clearance between the airbag mounts now less by the same amount the truck was riding on the bump stops inside the air bags. An additional piece of information - the truck is nowhere near contacting the spring perches for the factory overloads on top of the spring pack. In other words, I don't think a condition would ever have existed where the overload springs are engaged before hitting the air bag bump stops. Well, that's stupid.

I ended up putting about 40 PSI in the bags at this point to get the truck up off their bump stops, which worked, but defeated the purpose of taking out the extra leaves, the added air pressure raised the spring rate back up to an uncomfortable level. I needed to increase the distance between the air bag mounts (bump stops) so that I don't need so much air pressure to lift the truck off them.

I added some cheap lift blocks from Amazon to mount under the (shorter) spring pack to get back closer to original ride height and increase distance between the air bag mounts.

At this point, with about 10 PSI in the air bags the truck was riding far more comfortable. I could stop here and manually add air into the bags when the truck is loaded. Since I have a robust on-board air system I decided to go a step further. Since I am relying more on the airbags to be a more integral part of the suspension load capacity, I added a height control valve similar to Haldex type CR, mounted above the rear axle with a linkage to the axle and plumbed it accordingly. Add weight to the truck, the linkage activates the valve letting air from the on-board air system into the air bags, raising the truck back up. The converse is true, remove weight, leakage activates an air release and the truck lowers to its original state. I am using the "10 PSI ride height" to determine the neutral position on the valve.

I have some final clean up and fine tuning to do on the system. I'll be adding a pressure gauge to monitor air pressure in the bags and cleaning up some fittings that I don't like.

The goal of improving the ride comfort was a HUGE SUCCESS!

In hindsight the airbags were probably the biggest culprit, there is no way you could install them and maintain the original amount of suspension travel. If you are trying to decide if adding them is a good idea - don't. Also, the lift block kit I bought, I was able to use the block, but the U-Bolts wouldn't fit over the spring pack, they were too narrow.

Lastly, no need for "you shouldn't have bought a heavy duty truck..." I bought my truck to serve ALL my needs, towing large trailers AND riding comfortably. I could get used to the ride but my family matters too and they complained a lot.

doverarjim · November 6, 2025

I have the same truck as you but a long wheel base, I had the Kelderman Air Ride installed on it when new and it was the best money Ive spent on the truck. It will automatically level the truck when loaded or unloaded and the ride improved 100%

asilverblazer · November 6, 2025

13 hours ago, doverarjim said:

Kelderman Air Ride was the best money Ive spent on the truck. It will automatically level the truck when loaded or unloaded and the ride improved 100%

But the price though?! I'd be interested to compare our ride quality, I aslo wonder how much the added wheelbase would help.

If I had to replicate what I've done (which, I wouldn't buy the Airlift kit) I think it could be done for well under $2K including adding the on board air.

doverarjim · November 7, 2025

I had a 2011 2500 crew cab swb truck first and it rode ruff, next was a 2019 3500 crew cab lwb srw truck and stock it was better than the 11 truck as far as ride went, put the Keldermans on it and it was much better, when I traded up to the 22 crew cab lwb srw truck I put the air ride on it with in 5,000 miles of getting the truck and it rides better than the 19 truck did.

asilverblazer · November 10, 2025

Follow up to some of the finishing touches I added.

Simplified some of the air fitting coming from my main air line to the height control valve and from the valve to the air bags. Also added and electronic pressure sensor on the air bag line so that I can monitor air bag pressure.

I replaced the mechanical air pressure gauge with an electronic one that can read/display two sensors pressure readings. I can no monitor system pressure and air bag pressure both at the same time.

Whether by gauge discrepancies or other factors, rear air bags are running at about 20 PSI. I could adjust my linkage that determines ride height to fine tune the pressure/height/comfort level but I'll run it here for a while to see how I like it.

Chuck FB · December 18, 2025

On 11/10/2025 at 10:56 AM, asilverblazer said:

Follow up to some of the finishing touches I added.

Simplified some of the air fitting coming from my main air line to the height control valve and from the valve to the air bags. Also added and electronic pressure sensor on the air bag line so that I can monitor air bag pressure.

I replaced the mechanical air pressure gauge with an electronic one that can read/display two sensors pressure readings. I can no monitor system pressure and air bag pressure both at the same time.

Whether by gauge discrepancies or other factors, rear air bags are running at about 20 PSI. I could adjust my linkage that determines ride height to fine tune the pressure/height/comfort level but I'll run it here for a while to see how I like it.

The other day when I was looking for a place to put that information about the typical air bag kits that are often used on trucks, I found that older thread and plunked it there just so someone might come across it to warn them of the dark side of those kits and I had not seen this thread you had started.

It really is a tough task to have a suspension that can do everything, ride soft and smooth when unloaded and articulate well off road but yet carry substantial weight and still have a decent ride with suspension travel AND have the stability with a very tall center of gravity load in the truck such as a full sized camper with a basement that jacks up the total height of the camper to sometimes well over 12 feet high.

It would be interesting to see what a Kelderman air ride would do if it had a full sized camper slid into the back and I can see why that kit comes with an anti sway bar although I can't tell from the instructions as to what size it is but its interesting that it comes from Roadmaster.

Your 2018 diesel 3500, I haven't looked into it if those springs would be the same as my springs on my 2025 model gas truck with the same crew cab short box theme, in leaf thickness and count as well as the eye to eye dimension. I certainly won't make claims on my truck riding like a half ton !, and the fact that it has the 20" wheels would not be of any help as the sidewall height is shorter than what the factory 18" sized tires are. Also there is no getting around the fact that 10 ply tires won't ride like some wimpy 4 ply P rated tires, I just run the minimum air pressure that will carry the load of a near empty truck and being a gas means less pressure required in the front tires. That has made a huge difference as the factory pressures and with no surprise made what seemed like a reasonably smooth highway into one that every little hair crack in the road is felt.

My brother has an older F350 dually crew cab that he hauls a large slide in camper with and the truck has been dedicated to that for most of its life but when he first bought it he did a longer drive with it empty and was amazed at how nice it rode which was very surprising, but it also explained why it could not begin to carry the camper he bought properly with the factory rear spring setup even though it was supposed to. He had two more leafs added per side but he made the unknowing mistake of having air bags put in and that was the crux of part of his handling issues for years but did not realize they were largely to blame. He then bought those stable loads which are stupid expensive for what it there but never the less that made the main pack tapered overload spring engage the main pack much harder and he also put those rubber blocks on the frame brackets so the upper leaf could contact them sooner although Ford used a pathetic upper leaf back then. That certainly helped and helped more when he would drop the pressure in the air bags to a relatively low pressure and started realizing that while the airbags can carry weight, they take weight away from the leaf springs and allow for more sway instead. He still has the air bags on the truck but runs no more than 20 pounds i them. The other thing he did and I was the one that pushed him to do that even though that truck came from the factory with the camper special rear sway bar, was to buy the biggest sway bars he could and that seemed to be Roadmaster that made those, the front is a 1 3/8 and the rear is a 1 1/2 diameter. I don't recall the sizes of the factory ones but the rear one especially is way way larger. Between the stable loads ( and the extra leaves he ran from the time he bought the camper ) and those two larger sway bars, that is what that truck needed to carry as well as have good sway control as it was a danger driving that unit in side winds or around sharper curves before. The irony is that we both have our commercial drivers licenses and own highway tractors and trailers with air ride ( for farm use ) but the size and type of those spec'd suspensions on the tractors and for trailer applications seems totally fine, but that theme sure doesn't see to transfer over to these firestone bags in ride or stability.

But back to your modified suspension by pulling out that thick lower overload and the lowest thin leaf, that is interesting for sure in attaining a better near empty ride but I assume that would not play well at all if a tall camper was to be slid into your box, certainly not without a large sway bar but I would never rely on that air bag as you probably saw the video of what does happen to the bag mounts and frames will bend or fail if too much weight is applied in one spot without the frame being modified/beefed up.

asilverblazer · December 19, 2025

17 hours ago, Chuck FB said:

But back to your modified suspension by pulling out that thick lower overload and the lowest thin leaf, that is interesting for sure in attaining a better near empty ride but I assume that would not play well at all if a tall camper was to be slid into your box, certainly not without a large sway bar but I would never rely on that air bag as you probably saw the video of what does happen to the bag mounts and frames will bend or fail if too much weight is applied in one spot without the frame being modified/beefed up.

I wouldn't be surprised at that outcome either. Fortunately for me my circumstances/uses rarely involve high center of gravity loads in the truck bed. Most uses are only loading the truck at much lower points (goose neck, or bumper pull). The threat of sway (roll) is much less compared to the slide in camper use. It's hard for me to quantify how much sway (yaw) being induced from trailers might be prevented from the use of a dedicated sway bar. A fifth wheel hitch would also be an interesting comparison where the trailer could induce more sway (roll) on the truck due to its higher connection compared to a gooseneck since it would have more leverage.

Other thoughts, on my truck the airbags mount in the same location as the factory bump stops. Those points have to be engineered to accept some type of loading/impacts, but I have absolutely no way of determining what that number might be compared to what the air bags might be putting in those same locations. This is one of the reasons I left the auxiliary overload spring pack in place so that if I am loading the truck beyond the capacity (PSI my system is capable of putting in the bags) of the airbags they are still in place as a backstop.

More simply, I really don't anticipate a high enough payload on my truck to be concerned about the frame.

Chuck FB · December 19, 2025

4 hours ago, asilverblazer said:

I wouldn't be surprised at that outcome either. Fortunately for me my circumstances/uses rarely involve high center of gravity loads in the truck bed. Most uses are only loading the truck at much lower points (goose neck, or bumper pull). The threat of sway (roll) is much less compared to the slide in camper use. It's hard for me to quantify how much sway (yaw) being induced from trailers might be prevented from the use of a dedicated sway bar. A fifth wheel hitch would also be an interesting comparison where the trailer could induce more sway (roll) on the truck due to its higher connection compared to a gooseneck since it would have more leverage.

Other thoughts, on my truck the airbags mount in the same location as the factory bump stops. Those points have to be engineered to accept some type of loading/impacts, but I have absolutely no way of determining what that number might be compared to what the air bags might be putting in those same locations. This is one of the reasons I left the auxiliary overload spring pack in place so that if I am loading the truck beyond the capacity (PSI my system is capable of putting in the bags) of the airbags they are still in place as a backstop.

More simply, I really don't anticipate a high enough payload on my truck to be concerned about the frame.

Indeed tall slide in campers are probably one of the worst things as far as a top heavy weight that relies completely on the stability of the truck under it vs a fifth wheel to a lesser degree and a gooseneck trailer without too tall of a load less yet or bumper pull at the bottom of the ranking or so I would think. Certainly having good shocks is part of the key to keeping a truck in control when pulling a trailer. When you think about it, be it ether a goose ball system or a two way oscillating fifth wheel plate system, the trailer isn't able to force its leaning weight into the truck, only a side loading at the point of the trailers connection ( until the point of a side wind so high it tries to push the trailer over and the truck with it, best never to be driving in crap weather like that ! ). The Ram 2500's up to 2023 or so for example had a very low carrying capacity due to the soft coil springs, however they always ran a stabilizer because it must have been needed to attain a solid enough platform. Perhaps not a very good comparison to your lighter leaf spring setup but the concept of lighter springs and keeping sway to within reason. Of course if one looks at the spring packs on a GM 1/2 ton, its almost hard not to laugh when comparing them to the springs under an HD truck.

I wish the trucks were designed with more height between the frame and the axle tube although yes lifting the truck will accomplish that ironically but to be able to fit a different style air bag that had more travel and larger in diameter and then carry less pressure to do the same thing. Like you said, you end up bottoming out internally in the air bag at a higher truck height vs with the stock bump stops. And as to the upper overload pack to engage in time and not have the bag bottom out internally, one could install those hefty rubber blocks on the underside of the frame perches as it is rather strange how far away those perches are from the overload springs as the truck sits from the factory. I don't recall the brand but there is a brand of rubber block out there that is made to conform to the curved shape of the GM frame perches vs ones that are not and don't work satisfactory.

All I can say is that my brothers Ford F350 according to how he explained it as I was not in the truck when it was in such conditions, was with a side wind buffeting randomly on the side of the camper it would cause the truck to change course as in dart left or right and so one had to be on top of it constantly correcting the steering fighting to maintain direction and control of the unit and he said it was anything but enjoyable to be on a road with that rig in conditions like that and the thing is it didn't take some insane side wind to cause this. He had an older dually and camper prior and it was rock solid handling wise and I expect the added leafs it had in the packs helped as well, still a large camper but not as tall and probably not nearly as heavy as a srw 3/4 ton used to carry that same old camper. My brother was in for a rude awakening with this Ford and the camper he bought, it was a whole new world of crap your pants in windy weather LOL. I think you will know if you get into some side wind issues with lets say your bumper pull, if it seems to not do squirrely things when you hit some good side winds and also highway tractors flying by the other way or even the same direction, its probably a reasonably safe truck mod to be pulling the trailers you have. I believe that was also an issue with my brothers unit, tractor trailer generated winds or a combination of that and some side wind and the change in wind force as the truck passes. Going on a trip was a dread if there was wind encountered, now its become a non issue with any normal on the stiff side type winds.