Lift Options - 3500 Cab/Chassis - 37x12.5"

Trestle

Active member
I have a 3500 cab/chassis on order with the plan of a flatbed hard side camper build. I may put a popup in there temporarily as the hard sided options are booked out over a year. Reading about 2500 and 3500 Rams on this forum and trying to fit 37x12.5" tires it looks like there are three options. Carli, Thuren, AEV. I am hearing mixed info on the different lifts, but that is not the nature if this post. The post (at this point) is about options to fit the above tire size into this build.

It looks like the cab/chassis has some lift fitment issues. A call to AEV tech says their lift does not fit the cab chassis. No real explanation, more of a, "it won't fit, so get off my line so I can help someone else" answer. The funny thing is that Mario at AT Overland has a 3500 cab/chassis with 41s on it and an AEV lift. Perhaps this has something to do with it being a Gen 4.5 vs. Gen 4 Ram, but didn't get far enough with AEV tech to find out.

A call to Carli met no response and a VM. I'll try again later, but see below for a response from one of their retailers.

A call to CJC indicated that I may be able to use a leveling kit instead of lift kit, but pics are required to confirm. The call quality was crap, and there were constant interruptions, so it was a bit frustrating, but this is the gist of it. I won't have the truck until the beginning of July, so ordering the leveling kit through them in advance will have to wait. Carli Leveling kit is essentially a 2" coil lift up front, a 1" spacer out back, and a shock/steering track bar package. Then they say you can fit 37 x 12.5 with an AEV wheel (or similar offset), liner trimming, and pinch weld cutting. I like the AEV Salta wheels anyway, so that could work for me.

Here is the rough build info, as I don't know what items may be pertinent, along with the why of some of my choices for this build.

-'22 3500 single rear wheel, quad cab, cab/chassis, 60" C/A
-8' x 80" wide aluminum flatbed, no headache rack (plan to use a tunnel box for storage that will serve double duty as a headache rack, need the most storage from the tunnel box and a few inches counts here)
-SO Cummins - no real towing, so 800plus ft/lb seems more than adequate for my purposes
-Aisin HD transmission (lower first few gears to run 3.73 with 37's, not a lot of towing planned so hope to gain some fuel mileage back on the top end when cruising on flats)
-Dual 52 and 22 gal tanks (only offered in cab/chassis and I want the option of long range)
-Tradesman with few options (nicer radio, power seat, but rubber floor and mats) - can't hose it out, but not too far off from being able to
-Cold weather packages (I've lived from ID down to AZ, may never need it but not pricey)
-Power rear window (its a long way back there to vent the cabin for dogs)
-Vinyl seats (dog hair doesn't stick to them, and clean off easily)
-Bench seat (mostly travel with 2x, but nice to fit a third if needed)
-Delete rear seat (will build a storage system with platform on top for dog or dogs)
-115 outlet in cab - whoever is not driving can power laptop as we both can work remote
-Trailer brake controller - will tow some, just not any real weight, nice to have that option and like the integration into the dash
-Back up camera - there will be a camper on the back, so need to see rearward
-Keyless entry - surprised this is even considered an option and not standard
-Dual 220 amp alternators - plan to run a lot of lithium in the camper, want the option to charge it quickly, then supplement with solar

The main reason to go cab/chassis was to get the standard cummins with the Aisin tranny, and the 74 gallons of onboard fuel from the factory. Secondary was why pay for the bed if you're going to just pull it off immediately? Unsure if this was wise now looking at the possible suspension limit issue.

The flatbed, camper, fuel, water, gear, truck should be under GVW but not far off when we're geared up for a bigger trip. Eventually would like to use this truck for an Alaska to tip of Baja trip, perhaps longer trips later which could necessitate modifications (then not now) to allow for extended times without available ULSD. As is the range with both tanks should be in the 1,000 to 1,300 range. That should be plenty to get between fuel stops that don't have ULSD south of the US border.

The actual question is if anyone has more experience or information, options I may not be privy to, other suggestions to offer as it relates to putting this thing on our tire size of choice 37" x 12.5" (likely an AT such as the Wild Peak AT3). My guess is the aftermarket may catch up, or I may have to put together my own kit once I have truck in and and can make actual measurements. It would be nice to have something already sorted. I surely didn't anticipate this would be an issue with a cab/chassis over a standard unit, especially on the front end of the truck.
 

Zuber

Active member
Why not the standard Crew Cab, long bed with a bed?

You can sell the bed and tailgate. There is a box delete option for $100, but the bed/gate is worth $500-1500!! The pickup model has a boxed frame which is wider than the Cab/Chassis and stiffer. It has a 50 gallon tank, no option for the other 22 gal. But, you can put a 35" tire in the standard place between the frame rails (actually 34.5"). Everyone wants 37" tires, but there is very little advantage to them. The 35" are much easier to source and have a higher load rating and will fit on the std wheels with no other mods. With Method wheels and slightly hammering down one seam 37's will fit without a lift.

On a single rear wheel they usually install a 7 ft wide bed. This sticks out 3" past the cab on each side and looks ok. On the 60" cab to axle (8 ft pickup) you can install a 8, 8 1/2, or 9 ft long flat bed. Putting a flatbed on a Cab/Chassis or pickup is no different.

The Cab/Chassis has a narrow frame with a 'C' cross section to match all the other trucks from Ford/Chev. There's no room for a tire. Since you are talking about the Tradesman level, there's no real difference between them.

Look at the 'Snow King' option, well worth it. The 8.5" info screen is the right size, that comes in the Level 1 I think. I like the bucket seat option because of the huge storage in the middle.

My build from a few years ago using a custom ATC camper:

Popped R F.JPGFront Right.JPG
 

Trestle

Active member
Why not the standard Crew Cab, long bed with a bed?

You can sell the bed and tailgate. There is a box delete option for $100, but the bed/gate is worth $500-1500!! The pickup model has a boxed frame which is wider than the Cab/Chassis and stiffer. It has a 50 gallon tank, no option for the other 22 gal. But, you can put a 35" tire in the standard place between the frame rails (actually 34.5"). Everyone wants 37" tires, but there is very little advantage to them. The 35" are much easier to source and have a higher load rating and will fit on the std wheels with no other mods. With Method wheels and slightly hammering down one seam 37's will fit without a lift.

On a single rear wheel they usually install a 7 ft wide bed. This sticks out 3" past the cab on each side and looks ok. On the 60" cab to axle (8 ft pickup) you can install a 8, 8 1/2, or 9 ft long flat bed. Putting a flatbed on a Cab/Chassis or pickup is no different.

The Cab/Chassis has a narrow frame with a 'C' cross section to match all the other trucks from Ford/Chev. There's no room for a tire. Since you are talking about the Tradesman level, there's no real difference between them.

Look at the 'Snow King' option, well worth it. The 8.5" info screen is the right size, that comes in the Level 1 I think. I like the bucket seat option because of the huge storage in the middle.

My build from a few years ago using a custom ATC camper:

Zuber,

The truck is on order, and being built. The tray is on order and being built as well. The tray will be 96" long, 80" wide, and has no headache rack. The camper will have a 1' overhang off the back of the tray, angled to preserve some departure.

This tray setup, minus the headache rack, built specifically for a cab/chassis:
Screen Shot 2022-04-05 at 7.19.41 PM.png

Not knowing about the suspension situtuation I ordered the cab/chassis version to (1) get the 74 gal combined fuel for range. I may use the second 22 gallon tank only occasionally, but it will be available when needed. I also ordered it to (2) get the SO Cummings option paired with the heavier duty Aisin with lower gearing in the first few gears. This combo is only available in the cab/chassis that I can tell, at least on the '22 models. Top end for cruising (3.73 rear), lower first few to help move it (offset the 37s and 3.73) at close to GVW from a stop or in low speed situations. I'm sure some will argue, but I'm pulling this together from a few people that I put trust in as I have not owned a RAM before, let alone a diesel Ram with this much capacity. If I planned to go with 40's or bigger, I would have opted for the same setup with the 4.10 rear. I have no need for anything bigger than 37s for what we're doing.

Don't want buckets as there will not be a rear seat (building it out with storage and a platform on top for dogs). The bench is "like" a bucket setup most of the time with the folding storage down, with the option of putting a third person in the front on occasion. Storage in the rear seat box that I build will more than offset the loss in storage from the middle storage of the bucket seat. We may even add a small fridge in the cab built into it if the heights work out.

We did do the 8.4" screen. I wanted some creature comforts, and it seemed like a good compromise in terms if size, spend, utility. Will see once we get it, but hope I guessed correctly.

On 37's, the consensus from a half dozen people I am talking to on this is that they are the sweet spot on this truck for off-road capability vs. on road compromise. If I have to do 35s due to this situation, then that is where I will end up. I'd like to 37's if possible. I have had great experiences with the Falken AT3W tires, and want to use them on this build. They make a 37 x 12.5 that is D rated, and the max tire load for two tires is well beyond the max rear axle rating that RAM puts out for this model. 37's (vs 35's) would usually allow a lower pressure for a given weight as recommended by the manufacturer, so there is a little bit more compliance even before airing down. A 35 won't stuff between the frame rails on the Cab/Chassis, so my tire solution will be similar between the two tire sizes.

Based upon the pics (BTW, nice setup!) it looks like you have an older generation than the one we ordered. I've read on the CJC site (I think it was their site) that the 4.5 sit slightly lower from the factory than older generations. I have no way to verify this, and am hoping others with a gen 4.5 may chime in. It would be nice to keep the center of gravity down with a lower or no lift if I can still find a way to put my preferred tire choice in there.

One thing I noticed with AEV is that they recommending adding their front fender flare kit on top of their 3" lift to go from 37 to 40 or even 41s. I'm starting to wonder if I can do no lift and a fender kit with 37s, but it may look ridiculous. My guess is with the AEV wheels, or others with similar offset, one could reduce rubbing on the LCA, but it's all a guess at this point. I've always like the look of the F550 and 5500 front fender openings, but they likely stuff something appropriately sized in there to make things look proportionate. Since the rear tray has wheel fenders built specifically for 37" tires, I'm not sure if this will be a work around.

If you have info on which methods (size/offset) that may work with 37's and only seam/liner modification, I'd appreciate that information. I like method wheels, and their hybrid beadless solution for retaining the tire on the rim at lower pressures is appealing too.

Thanks again,

Don
 

Zuber

Active member
I have the Method 701 Trail series wheels from Carli's recommendation of 18mm offset, 18x9 wheels, forged aluminum with the bead retention grooves. These have a 4500# load rating, the highest I could find. The AEV wheels were wrong for some reason, lower weight and/or offset.


The Carli drop brackets will move the front axle forward about a 1/2", so 37's clear. Carli's trailing arms give more clearance too. But, you said it doesn't fit the Cab/chassis.

In the pickup models, I don't think there were any changes in suspension from 2014-up. Most of the changes for the 4.5 gen was the cab interior. The 2021 got the better fuel pump, yeah!.

If you are close to the max GVW all the time, the Aisin transmission is a great choice. Running empty it feels a little rough, but it's a big tough one.

The pictures were of my old 2013 2500 flatbed setup. I bought the camper bare and fitted out the interior. Now I'm going different with a 2021 2500 Ram and canopy to replace my Jeep and in 6 months a 2022 Earth Cruiser Terranova on a 3500 Cab/Chassis Ram with the dual tanks. I like RAM and the Cummins. These are my 4th and 5th models.
 

Superduty

Adventurer
I had some Carli questions and after striking out with Carli and CJC i got great tech info from Top Tier Suspension. They sell a lot of Carli products and the guy i spoke to was knowledgeable.

Sent from my SM-G973U using Tapatalk
 

Klutch7

Member
I may be wrong, but since you ordered a 3500 CC, I believe the front suspension is the same as a standard 3500 truck. This means that any kit from Carli or another manufacturer will work for the front. I like the Carli products. Thuren Fabrication is another reputable shop to call. https://www.thurenfabrication.com/ They got their start on the Dodge HD trucks.

Regarding the rear, I think this is where the CC trucks differ from the standard due to the different frame section (this is at least true on the Fords). I think your best bet would be giving Atlas Suspension or Deaver Spring a call. I'm sure either of them could build a custom spring pack for your application with some measurements provided by you.
 

Trestle

Active member
@ Zuber
I wanted the diesel for range, and the difference in fuel mileage when loaded. The difference empty between gas/diesel doesn't seem to offset the additional costs. When heavily loaded, pushing lots of wind, or both the diesels tend to make more sense for us. That and we plan to keep it long haul. Our lowest mileage vehicle right now is at 165k, so we get mileage our of our vehicles. If going gas, we'd be looking at the F350 with the 7.3 and 10 speed. For diesel, I think the simplicity of the Cummins as compared to the Ford 6.7 is what we like the most. I wish they had an 8 or 10 speed behind the Cummins though. It will probably come out next year, cause well I just bought one.

@ Tex68w
Reached out to them today. They were helpful, and I will detail where we are at further below in this post.

@ Superduty
Reached out to Top Tier Suspension. Really helpful, and glad to have the suggestion.

@ Klutch7
You are likely correct about the 3500 front end, or at least Top Tier Suspension and Thuren think so. They still recommended waiting until the truck arrives, and to take pics to confirm everything.
____________________________

Pending confirmation with the actual truck, here is where the information is at right now.

It looks like the 4500 and 5500 use the older suspension setup in the front. When I said 3500 cab/chassis to AEV and CJC their heads probably went to the 4500 and 5500s when telling me the trailing arms or drop bracket solution wouldn't work on the front of a 3500 cab/chassis.

Top Tier further indicated that even if the 3500 cab/chassis followed the same format as the 4500/5500, then we could still lift the front using the kit for older Rams. In essence, you just have to pick the correct one, get 3 or gen 4 front end lift.

Rear suspension on all the cab/chassis are indeed different. Likely less travel, perhaps different shock lengths, and in a different location. Top Tier indicated they would find a rear shock solution once we could take measurements.

Assuming all of this plays out as I see it today, we are leaning towards a Carli pintop 3.25" system with modified rear shocks as needed once measured. Retention of the factory rear springs plus a spacer since we will be at or within 1k lbs (probably only 500lbs under) of GVW most of the time. I'm impressed with how many questions that Top Tier asked, to get to the specifics of what we are after. Zack asked what we were thinking for nearly each aspect, why we were thinking it, the offered advice accordingly. Very knowledgeable, and I plan to run my business through them once we have truck in hand.

I will do an update for the sake of having this knowledge on the forum for others to benefit from as it plays out.

Really appreciate people's involvement and input.

Don
 

rruff

Explorer
The truck is on order, and being built. The tray is on order and being built as well. The tray will be 96" long, 80" wide, and has no headache rack. The camper will have a 1' overhang off the back of the tray, angled to preserve some departure.

This tray setup, minus the headache rack, built specifically for a cab/chassis:
View attachment 715938

If the pickup version has a fully boxed frame (as Zuber stated) and the CC is C-channel, these are night vs day different structurally... the pickup frame very stiff, and the CC very flexible torsionally. The stiff frame makes mounting a bed and camper much easier, as it can all be hard-mounted with no worries. But a flexible frame needs either pivots or spring mounts between chassis and subframe, or you will have problems with an off-road rig (things eventually breaking) where getting "crossed-up" is a common occurrence.

After a brief look here I don't see any mention of isolation provided in the bed: https://setoverland.com/full-size-pickup-trays-flatbeds/

Some discussion (too much?) of options for chassis/subframe isolation: https://expeditionportal.com/forum/threads/pivoting-frames-and-mounting-campers.25494/page-42
 

Zuber

Active member
I don't think you'll see a 8 or 10 speed behind the Cummins, because it just doesn't need it and you won't miss it in the real world.
 

Trestle

Active member
@ rruff
Thanks for the reminder. I'm familiar with the concern, three point & four point sub frames, some of the remedies used in Australia, and issues with broken frames (fusos) due to not taking into account or allowing for flex. Once the flatbed is mounted, and lift sorted out, it is a matter of flexing the combination to see just how much deflection is present in the real world. Then design accordingly adding in a little headroom. It is amazing what one can do by pinning the front (or rear) of a structure for minimal movement, and then using the same type but longer hardware on the opposite end with spring loaded give to account for actual measured flex. Then there is the camper design. I'll set my level of concern once I see just how much the combination flexes in the real world.

@ zuber
Compared to my 2wd sprinter with much less power, a 5 speed tranny, and oversized tires that are a whopping 32" set at 65 psi, I'll just have to suffer with this new rig if they do happen to come out with more gears after the fact. Somehow I'll muster the will to go on. First world problems!
 

Tex68w

Beach Bum
While there has been much talk/speculation of a Allison or ZF 8-speed ultimately coming to the Cummins platform, I simply don't see the need.
 

Darwin

Explorer
For reference, my (sold) 2018 3500 C/C has the newer suspension design trailing arms, and my 2021 5500 has the older style.
 

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