ATB A-CG51 aluminum underbody cargo toolbox, smooth body with diamond tread side-opening door, closed
ATB A-CG51 aluminum underbody cargo toolbox, smooth body with diamond tread double side-opening doors, closed
ATB A-CG51 aluminum underbody cargo toolbox, double side-opening doors open showing interior
ATB A-CG51 aluminum underbody cargo toolbox with double side-opening doors installed under a semi trailer

ATB A-CG51 Underbody Cargo Box, Aluminum Side-Open Doors, Dolphin Tail T-Handle Lock

$1,312.50
Freight shippingCalculated at checkout Only 1 leftIn stock now  Estimated delivery
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Free gifts included with your order

Details
Details
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  • 30-Day Money-Back GuaranteeReturn it within 30 days of delivery for a refund
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Features

  • .125 Aluminum Build: ATB builds the A-CG51 from .125 aluminum: a smooth aluminum body with a diamond tread plate door. ATB calls it super heavy duty.
  • Seam Welded, Gusseted: Fully seam welded on all seams and corners, with gusseted corners for added strength.
  • Side-Open Doors: Side-open doors on full-length stainless-steel continuous hinges; the 36"-wide size has double doors.
  • Dolphin Tail T-Handle: A lockable stainless-steel dolphin tail heavy-duty adjustable T-handle latch secures the door.
  • Rain Gutter & Seal: A fully concealed rain gutter with an automotive weather seal helps keep tools, tarps and gear dry.
  • Under-Trailer Mounting: Mount it under a trailer deck or on the back of a truck; the mounting kit is sold separately.

Description & Fitment

The ATB A-CG51 side-open cargo box is a long, high-capacity aluminum box for under a trailer deck or the back of a truck, with doors that swing open to the side. ATB builds it from .125 aluminum with a smooth body, diamond tread doors, stainless-steel continuous hinges and a lockable dolphin tail T-handle latch. Three sizes run from 72" to 101" deep, and the 36"-wide box has double doors.

Fitment & Compatibility

How to choose: measure the clear length under the deck or on the frame for depth (72" to 101"), then the drop below the deck for height and the room you have for width.

Leave swing room beside the box for the side-open door. ATB offers optional gas springs and a full-length shelf; contact us before you order.

Fits: Under a trailer deck or truck body (check length, drop and width)

About ATB

ATB

American Truckboxes (ATB) builds aluminum and steel truck boxes, tanks and storage in Blanchard, North Dakota, and has done so for more than 25 years, by its own account. Its range covers pickup crossover, side-mount, chest and drawer boxes, service-truck boxes and packs, fuel tanks, and heavy-truck and trailer boxes.

Authorized ATB dealer. Prestige Truck is an authorized ATB dealer: every box on this page is built by ATB to the part number shown.

Frequently Asked Questions

Will it fit my trailer?

Fit is by space, not by model: compare the clear length, drop and width under your deck with the sizes in the table.

How do I measure for an A-CG51 cargo box?

Sizes read height x depth x width. Depth is the long side (72" to 101") that runs along the trailer or truck; measure the clear space under the deck or on the frame, plus room for the side-open door to open.

Is a mounting kit included?

No. ATB lists its M2600UD under-deck/trailer brackets for this box and the M3452C kit for frame mounting; both are sold separately.

How many locks does it have?

One. ATB fits a single lockable stainless-steel dolphin tail T-handle latch on boxes under 38" wide, which covers every size on this page.

Is the box weather sealed?

Yes. ATB builds in a fully concealed rain gutter with an automotive weather seal around the door opening.

Can I get a smooth or mirror door, or a custom size?

ATB's standard door is diamond tread; smooth or mirror doors, steel construction and custom sizes are made to order. Contact us for a quote.

Installation

Install time About 1.5 to 4 hours
What's involvedRod bolts and clamp brackets hang the box from the trailer cross beamsyou drill 1/2" holes per ATB's M2600UD sheet.
Tools
  • 3/4" ratchet wrench
  • 3/4" wrench
  • Tape measure
  • Drill with 1/2" bit
  • Two clamps
  • Blocks

Here's the short version. Follow ATB's install sheet (below) for your truck's exact positions and hardware.

  1. Check all parts against the parts list and make sure there is room to mount the box.
  2. Move the cargo box to its underbody position to check it fits there.
  3. Move the box aside. Put a washer and locknut on each rod and tighten until the thread shows 1/4" past the nut. Slide each rod through a top bracket and fit the top clamp bracket between the trailer I-beams. Do this for all brackets before going on.
  4. Set the outside brackets as far out on the trailer as possible and one in the center (ATB: three bracket sets for 750 lbs., five for 1250 lbs.).
  5. Fit the top bracket and top center clamp, insert the bolt with a washer on both ends and secure it with a nylon lock nut, then secure the nut on the rod.
  6. Move the box into position and block it in place.

Stuck on a step? Ask our install experts

What's included
  • A-CG51 aluminum underbody cargo box with side-open door(s)

Specifications

BrandATB
TypeUnderbody cargo box, side-open doors
Material.125 aluminum
ConstructionFully seam welded, gusseted corners
FinishSmooth aluminum body, diamond tread plate door
HingeStainless-steel continuous hinge
LockStainless-steel dolphin tail T-handle latch, lockable (one lock)
Weather sealConcealed rain gutter, automotive weather seal
Mounting kitNot included (ATB M2600UD under-deck kit; M3452C for frame mount)
Made inUSA
Part numberA-CG51-187218SL-T
Versions
Part # Size Door Door opening Weight
A-CG51-187218SL-T 18"H x 72"D x 18"W Single side-open 14-3/8"H x 14-3/8"W 80 lbs.
A-CG51-188424SL-T 18"H x 84"D x 24"W Single side-open 14-3/8"H x 20-3/8"W 108 lbs.
A-CG51-1810136DL-T 18"H x 101"D x 36"W Double side-open 14-3/8"H x 30-3/8"W 172 lbs.

Warranty, shipping & returns

  • Warranty

    ATB covers its standard truck boxes with a 60-month (5-year) limited warranty for the original purchaser; it is not transferable.
    • For a warranty claim, contact us with your order number and photos and we will work it through with ATB.

  • Shipping

    Ships by freight from the ATB factory in Blanchard, ND; lift-gate delivery available.
    • Alaska, Hawaii and Canada: contact us for a freight quote before you order.
    • We email your tracking details as soon as it ships.

  • Inspect on delivery

    Check the box when the freight arrives, before the driver leaves: look over the lids, doors, corners and welds for dents, scratches or shipping damage. Note any damage on the delivery receipt and send us photos. Check it as soon as it arrives.
    • Look for crushed ends, punctures or tears in the carton.
    • If something looks wrong, take photos of the box and the parts (and if a driver asks you to sign, note the damage on the receipt).
    • Open the box and check the parts against the parts list before you install.
    • Email support@prestigetruck.com right away with your order number, a short note and photos. We send a replacement or a full refund at no cost to you.

  • 30-day returns

    Return it within 30 days of delivery, unused, in the original packaging, with proof of purchase.
    • Email support@prestigetruck.com with your order number. We reply within 1-2 business days with instructions.
    • Damaged, defective or wrong item: we send a prepaid label or arrange a pickup.
    • Changed your mind: you pay return shipping. No restocking fee.
    • Refunds go back to your original payment method within 7 business days of approval. See our returns policy.
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