Triple - Dual Wheel Gooseneck Trailer

Model: FMAX312

GVWR: 30,000 - 40,000 lb

With an up to 40,000 lb GVWR, 18″ Engineered Beam frame, and 9,000 lb curb weight, the FMAX312 triple dual wheel gooseneck trailer is the undisputed king of the road. This gooseneck trailer sets the benchmark for strength and capacity, making it the ultimate choice for heavy-duty hauling.

Build Your Own Trailer

At a Glance

GVWR: 30,000 lb (w/ optional 40K Upgrade)
LENGTHS: 25′- 44′
WEIGHT RANGE: 8,330 – 13,080 lbs
BED WIDTH: 102″
FRAME: 16″ – 18″ Low Profile Engineered Beam
NECK: 12″ Curved Engineered Gooseneck
AXLES: 3 – 12,000 lb Lippert Axles
TIRES: 14 Ply All-Steel Radials
(Upgrade to 215/75R17.5 – 18 Ply)

FMAX Engineered Beam Technology & Logo

NEW FLEETNECK 2.0 FEATURES

New, Lighter Neck

The Fleetneck 2.0 neck web is stronger and lighter with the new 10-gauge Grade 80 material resulting in a 65-pound weight reduction.

New Spare Mount Location

The new spare tire mount location with the easy-to-handle winch that raises and lowers the spare is now located under the trailer deck, guaranteeing it is out of your way until you need it.

Grade 100 Beams

Grade 100 main frame beams with a 10-gauge thickness have doubled the yield strength of the Fleetneck 1.0.

Chain Tray/Winch Mount

Storing your chains is easy with the standard chain tray with a winch mount combination and has the option to add a bolt-on winch box.

Engineered Beam Technology

We design, engineer, and build our own I-Beams. Our U.S. Patent Protected Engineered Beam design allows for the tallest and strongest beams in the industry, with the best strength-to-weight ratios on the road.

Taller beam. Lighter Weight. Stronger Frame.

READ MORE

Diamond C Air Ride

BENEFITS OF AIR RIDE

Ride Quality & Cargo Protection: Smoother & quieter ride that protects the cargo being hauled.
Standard Bolt-On Front Lift Axle: This unique included feature saves tire wear and fuel consumption on empty hauls.
More per mile: Air Ride allows you to net higher rates per mile hauling loads not allowed with standard suspension.

LEARN MORE

FMAX Overview Diagram
  1. The Neck – Curves distribute force throughout the neck so there is no concentration of stress in corners like traditional goosenecks.
  2. The Deck – It’s low profile for easy access. Tire-covers are HD 3/16” diamond plate. Boards are capped at each end of the deck for added durability.
  3. The Camber – The deck and frame have a slight camber when not loaded. When loaded, it flexes as necessary to level but never sags like traditional goosenecks.
  4. The Lace-rail – Channel-Iron for durability and versatility with no notches or cut-outs for maximum strength. Includes stake-pockets and pipe-spools.
  5. The Box – It’s big and roomy. The lid is curved for added rigidity and gas spring assisted for easy operation.
  6. The Steps – The retractable front deck steps solve the common issue of traditional front deck steps being bent in low clearance situations. The mid-deck side turn signal step makes for easy access when equipment is loaded.
  7. The I-Beams – We engineer the beams, optimize them, and build them for each trailer configuration just like semi trailer manufacturers have been for decades. Our I-beam frames are taller, stronger, and lighter than your neighbor’s. 14-18″ tall. Standard steel bends at 36 ksi. Our beams are built using steel rated at 50 ksi minimum.

Loading Your Way

Max Ramps

Max Ramps

44″ wide ramps for MAX versatility. 50 ksi steel ramp frames x 4 frames per ramp for MAX strength. HD Spring loaded for easy lifting. For safe, stable loading. Read more HERE.

12' Hydraulic Dovetail

12' Hydraulic Dovetail

12′ long with easy to climb, 12.5 degree approach angle. Includes Blackwood rubber-infused runners for traction, automatic latch for easy operation, and wireless remote control. Read more HERE.

XDR Ramps

XDR Ramps

These 24″ x 60″ spring-assisted extreme duty knee ramps are perfect for loading concentrated machines such as backhoes and excavators where space between the ramps is a necessity for knuckle height clearance. Read more HERE.

FMAX Straight Deck

Straight Deck

The Straight Deck tail configuration includes 3″ channel 96″ Rear Slide-In Ramps that can be conveniently stowed away when not in use. Come with a single piece bumper with light protection.

Find a Trailer Dealer Map

How Do I Order an FMAX312?

Great question! Keep scrolling to customize and build your FMAX312 gooseneck trailer to your liking with our interactive build-your-own trailer configurator, then you will be prompted to submit your trailer build to your nearest Diamond C dealer for quote and availability. We have an extensive dealer network of almost 200 dealers strategically placed throughout North America.

Popular Upgrades

3

40,000 lb GVWR Upgrade

When only the very best will do, upgrade your FMAX312 to our heavy duty 40K Package. Includes a 3″ ball ADJUSTABLE COUPLER and frame/neck reinforcements for maximum strength. #DoWork

Dual 20K Hydraulic Jacks

A must have for anyone who hooks and unhooks their trailer often! Fast, convenient, and strong. Learn more HERE.

Quality Trailers Since 1985

Diamond C has been an industry leader for over 35 years since our humble beginnings over 3 decades ago. We strive to be on the forefront of trailer manufacturing by continuously demonstrating excellent quality and value, cutting edge innovation, and superior customer service.

Design Your Own FMAX312

More Than Just A Trailer

Crabb Family

Family Owned and Operated

Over 39 years ago a young East Texas couple embarked on a journey that at the time was merely a means to put food on the table for their growing family. Unbeknownst to them, their nature would have an endless impact on the business they would create…

OUR STORY

Diamond C Team Members representing the Core Values

This is who we are and what makes us Different

Our Purpose is to fuel the growth and success of Diamond C team members, our customers, and our community.
Our Niche is extraordinary trailers and service to match.
Our Core Values are Do Work and Love Strong.

LEARN MORE

DM Powder Coating System

Our custom Difference Maker DM COATING SYSTEM produces extraordinary trailer finishes that are exceptionally durable and beautiful. We offer multiple standard and custom COLORS to perfectly compliment your trailer.

Watch Video

Learning Center

Your one-stop-shop for everything trailer related. In-depth resources (like our GOOSENECK TRAILER BUYER’S GUIDE) and articles about our trailers, options, culture, and what makes us stand apart from the other guys.

CHECK IT OUT

Maximum Customizability

Choose from a variety of upgrades:

HYDRAULIC JACKS
BLACKWOOD LUMBER FLOORING
SHOCKER HITCH COUPLER
SLIDE TRACK & RATCHETS
CUSTOM COLORS
– and more…

The choice is yours.
Configure your ideal trailer below.

Custom Paint Color Lime Green
Sheffield and Synchrony Logos

Finance Your Trailer

Finance a brand new FMAX312 with ease through one of our trusted financial partners. Find out more HERE.

Diamond C Warranty Logo

Quality You Can Trust

We are proud of our trailers and stand by them. Every Diamond C trailer comes with an industry leading 3 Year WARRANTY.

3 Easy Steps to Build Your Own Trailer

  • Step 1

    Configure your ideal trailer below by selecting your desired specifications.

  • Step 2

    Submit your custom trailer build to your closest Diamond C dealers.

  • Step 3

    Your selected dealer(s) will contact you with final pricing and availability.

Base MSRP: $35,734

*Trailers are shown with base MSRP pricing (Manufacturer’s Suggested Retail Price). MSRP is NOT final sales price - your final sales price varies depending on region and dealer. Be sure to submit your trailer to your local Diamond C dealer for final trailer pricing.

Model

Loading Style

Max Ramps

44" wide ramps for MAX versatility. 50 ksi steel ramp frames x 4 frames per ramp for MAX strength. HD Spring loaded for easy lifting from deck and from ground. For safe, stable loading.

Watch Video

Price: $0.00

X
XDR Ramps

24" Wide x 60" Extreme Duty Knee Ramps. These spring-assisted ramps are perfect for loading concentrated machines such as backhoes and excavators where space between the ramps is a necessity for knuckle height clearance.

Watch Video

Price: $0.00

X
12' Hydraulic Dovetail

12' long with easy to climb, 12.5 degree approach angle. Blackwood rubber-infused runners for traction. Automatic latch for easy operation. Includes wireless remote control.

Watch Video

Price: $0.00

X
Straight Deck

Includes 96" Rear Slide-In Ramps (3" Channel). Single piece bumper with light protection.

Price: $0.00

X

Length/Width

Price:

GVWR

Includes 3 - 12,000 lb Lippert Axles

Price: $0.00

X

Includes 3" Ball 40K Adjustable Coupler and Frame/Neck Reinforcements

Price: $2,673.00

X

Need 40K GVWR? Select a 30' or longer model above

Ramps

96

Price: $0.00

X

Dove

60

Price: $0.00

X
Wood Filled Dove/Ramp

Ideal for loading equipment with steel tracks.

Watch Video

Price: $644.00

X
60

Price: $0.00

X
12' Fully Automatic Hydraulic Dovetail

12.5 degree load angle with Blackwood infused lumber and automatic latch.

Watch Video

Price: $0.00

X
Full Steel Runner with Cleats

Price: $468.00

X

Price: $363.00

X

Axles

3 - 12,000 lb Heavy Duty, Oil Bath Logo

Price: $0.00

X

Brakes

Electric Drum

(Forward Self-Adjusting)

Price: $0.00

X
Electric-Over-Hydraulic Disc Brakes

Price: $4,400.00

X

Suspension

6-Leaf Slipper Springs, 48

Price: $0.00

X
Hutch Heavy Duty Adjustable Suspension

Features easily adjustable torque arm screws, a maintenance free fastening system, and "Million Mile Rocker Bushing" which eliminates bushing fatigue and failure.

Price: $1,436.00

X
Air Ride Suspension with Front Lift Axle

Custom designed Cush Air Ride System. Includes dual compressors, one 10V 5amp charger and dual Group 27 continental batteries.

Watch Video

Price: $14,691.00

X

Want Air Ride? Select a 35' or longer length

Want Air Ride? Select a 35' or longer length

Air Ride Suspension is not available on this length Hydraulic Dovetail or Straight Deck triple axle model. Please select a 35' or longer length above to view Air Ride options.

Price: $0.00

X

Pull Type

12

Curves distribute force throughout the neck so there is no concentration of stress in corners like traditional goosenecks.

Price: $0.00

X
6

This option raises the coupler and horizontal neck height +6". Ideal for lifted vehicles (ex. Dodge 3500 with 4"-6" lift) or Semi-Tractor applications.

Price: $237.00

X

Frame

16X
18X

Jack

2 - 12,000 lb Drop-Leg Jacks

Two heavy duty, square, drop-leg trailer jacks with a side-wind handles. Constructed of engineered alloys for enhanced strength, stability and side-load capability.

Price: $0.00

X
2 - 25,000 lb Two Speed Drop-Leg Jacks

Price: $1,425.00

X
2 - 20,000 lb Hydraulic Jacks

A must have for anyone who hooks and unhooks their trailer often! Fast, convenient, and strong.

Price: $2,150.00

X

A must have for anyone who hooks and unhooks their trailer often! Fast, convenient, and strong.

Price: $1,555.00

X

Model

Tire Size

Price: $0.00

X
215/75R17.5 18 Ply Radial, Dually

Price: $1,875.00

X

Wheel Color

Black

Price: $0.00

X
Aluminum Outer Wheels

Price: $745.00

X
Aluminum Outer Wheels


Price Descriptor:

$1120 $250 - Limited Time Special!

X

Spare Mount

Under-Frame Spare Mount

Price: $0.00

X

Spare Tire

Price: $335.00

X

Price: $335.00

X

Price: $455.00

X