Truck Bed Trailer Simulated in 3D Cad Solid Modeling Software (Click on Image to see a larger version)

This post will summarize the key points in creating a truck bed trailer:

1. Carefully determining where to cut the frame of the truck bed so that it rides level to your truck and has appropriate ground clearance for your needs.
2. Setting up and cutting for the appropriate angles when using an A-Frame coupler on the tongue.
3. Getting the alignment right from tongue to axle and rear of the truck, so the trailer tracks perfectly straight.
4. Other tips such as inexpensive tools, wiring ideas, tongue jack suggestions, etc.

This is a fairly straightforward project if you have a welder, some good skills with an orbital jigsaw, the right safety equipment and procedures, and some energy to do it (not to mention the truck).

Donor Truck: `86 Dodge D-150, previously Propane powered.  Propane tank is still in pickup bed of truck in photos.  Front half of truck frame was donated to `67 Dodge D-100 Hemi Truck project.

What a shame we cut this thing up, considering it drove over to my house! Luckily no parts were wasted. (click photo to enlarge)

For this project, we chose to purchase 6″ x 2″ x 0.125″ rectangular tubing.  This was a very close match to the `86 Dodge Truck frame C-Channel size, which is just larger than 6″ by 2″ when cut just in front of the truck bed.

We chose not to cut and bend the existing truck frame to make the trianglular front frame section.  This is because the `86 D-150 frame (and just about any other pickup truck frame) gets lower (drops down closer) to the ground underneath where the cab was.  If we had bent and welded the frame, it would have been lower to the ground, requiring a drop hitch on the puller truck.  The method we chose did not require a torch to bend the frame, but it did require extra cutting, careful setup of the angles, and more welding.   Either method works just fine, but ground clearance is maximized with this design and there’s no major manhandling of metal.

We also kept the original truck rear differential, it was a Chrysler 9 1/4.  Just filled it up with fresh lube and put the cover back on.   Note: You can also put a straight axle under one of these trailers.   I’ve even seen people weld up the spindles on old, steerable single i-beam front axles from old pickup trucks to accomplish this.  We didn’t have a need for the rear differential nor did we have the time to mess with swapping it out.

The truck bed will not have brakes unless you swap out the hydraulic brakes for electric, which would probably require some serious modifications.  The bolt pattern on `80s and up Dodge trucks is 5 x 5.5  and most trailer brakes are 5 x 4.5 like the older Mopars.  It would take some pretty decent fabricating and modifying to get electric brakes to work unless you found some that could work inside the existing drums.  We also didn’t investigate this.

Pre-Build note:  The angle between the flanges of an industry standard A-Frame coupler is commonly 50°.  This means that each of the frame rails in the triangle will be 25° from the centerline, and that the cuts between the straight frame rails (welded to the truck frame) and the angled rails (welded to the a-frame coupler) need to be 12.5° from perpendicular (or 77.5° as measured between the long side of the rail and the cut) on each mating part, to make the 25° angles.  See also the attached sketch below:

CAD Drawing of actual dimensions used in this project. Take a close look at the angle dimensions to understand what I mean by the 12.5° angles (click image to enlarge)

Step 1 - cut the frame rails off the donor truck, leaving approximatey 3 inches of frame stub in front of the bed and any crossmembers to allow for welding.

Step 2 - Gather up the tubing or c-channel for the straight and triangular frame rails at the front of the trailer.   Plan out how long you want the rails.  For this design our straight rails in front of the trailer were rather long, approximately 22 inches (see drawing above).  The thought was that we could bolt on a big tool box later, in front of the truck bed and behind the triangular section.   Or maybe put some Motorcycle channels in and carry cycles directly on the frame, with parts and junk in the truck bed.

Example of 12.5° Angle cut into 2" x 6" Rectangular tubing (click photo to enlarge)

Step 3 - Cut the tubing to length, then cut the mating sections at 12.5° angle from center.  This can be done with a protractor and some careful work with a sharpie pen.  We actually did the major cutting with a orbital jigsaw, then cleaned it up with a grinder.

A-Frame, mocked up on the floor prior to any welding (click photo to enlarge)

Step 4 - Mock up the A-frame tongue.  Measure twice, cut or weld once!  We did some rough clamping and measuring on the floor as you can see in the above photo.

Fixture or Jig built onto workbench (angle between wood pieces is 155°, to accomplishn 25° angle between framerails). Click to enlarge photo.

Step 5 - Build a fixture or jig to properly position framerails for welding.  I bolted some wood to my workbench to accomplish this.  See above photo.

Framerails inserted into Fixture/Jig and tack welded. (Click to enlarge photo)

Step 6 - Insert the frame rails into the jig.  Tack weld the framerails.

Both side a-frame rails slid into the truck frame in this photo. All parts have been tack welded. (Click to enlarge photo)

Step 7 - Clamp the rails to the front of the truck.  Clamp on the a-frame coupler.  Run a string from the rear center of the truck bed (underneath the tailgate) all the way to the a-frame coupler at the front.  If the string is taught, it should line up with dead center at the middle of the trailer at the front of the truck bed.  Adjust the assembly and clamp until perfect.  Once the string is on center from front to back, tack weld everything together on the truck.

Step 8 - Re-measure everything and double check your centerline with the string.  If everything checks out, weld it all up!!!!!

Step 9 - Sand down and clean all of the metal, then paint the a-frame tongue.  Makes for a good impression at the DMV when you have to register the thing.  I recommend the professional version of Rust-Oleum rattle can paint, it works the best and lasts a long time.  Be sure to wear the proper mask to prevent inhalation of fumes.

Freshly painted Trailer Tongue. We welded on a side mounted tongue jack, but an a-frame jack would have been more stable when the trailer is parked. This was just cheap and quick/easy. (click photo to enlarge).

Step 10 - Wire up the rear taillights of the original truck.  This is best because they are already on the truck, you don’t have to go buy other lights or bolt up something cheesy.  More often than not, when I’ve seen homemade trailers the origina lights aren’t hooked up and someone has bolted on additional lights.  No need!!

Step 11 - Get the trailer registered.  Check your local DMV web – site.  It was actually not that big of a deal for us.

Nothing better than a Dodge trailer mated to a Genuine Dodge Truck! (Click photo to enlarge)

Step 12 - Load up your trailer, hitch it up, and away you go.

Looks happy, doesn't he? Not bad for spending about $150 on frame rails and an A-frame coupler! (Click Photo to Enlarge)

Lighting/Electrical:
The trailer had to meet all highway lighting requirements for trailers, which included side running lights at the front, and stop/turn/tail lamps at the rear.  We rewired the original `86 Dodge D-150 tail lamps via original harness to a four wire harness plug to enable lighting on the trailer.  Since the total width of the truck bed did not exceed 80 inches (it was about 77 or so), it was not required to add the set of three red lamps at the center of the rear of the trailer.  I guess if you made a trailer out of a dually truck bed it would be required since the total width including the dually fenders would be more than 80 inches.

To get this homemade truck bed trailer registered in the State of Nevada, I had to have:
-Receipts proving that I purchased at least 50% of the materials, and/or
-copy of the title for the original truck which was dismantled to make the trailer.

From there, the DMV inspection station had to issue a State of Nevada VIN number which was applied via decal.  The VIN was also stamped into the frame, right there, on-site at the DMV.  It’s just a trailer!!!  But, they insisted, its the rules.  At least they don’t require insurance on trailers.  All in all it was relatively easy.

Copyright Kris Wickstead ©2009.  Always use good sense, the proper safety procedures, PPE and safe equipment.  Follow all manufacturers instructions.  For informational purposes only.  Not a guarantee of any kind.  Use information at your own risk.

Keywords:  How to register a home made (or homemade) utility trailer in the state of Nevada.  How to build a pickup truck trailer or pickup truckbed trailer or truck bed trailer rv a-frame a frame coupler.