The 5th gen 4runner has a 1.5 inches in between the rear cargo height and the height of the back seats when they are folded down. It’s a little annoying when you are transporting stuff, but it’s a real issue when you are trying to sleep back there if you are camping or overlanding. I set out to build a small false floor in my cargo area to level the platform out and ended up finding almost 3 additional cubic feet of space hiding under the carpet.
If you don’t have the 3rd row seating or the fancy sliding cargo tray, you have a solid chunk of nearly 2 inch thick foam under the cargo area carpet. If you pull that out you have nearly 4 inches from the floor board to the height of the rear seats when they are folded down. That’s a lot of space for activities!
I don’t have a lot of space for woodworking things, so this was all built using a circular saw, a jig saw and one of those vibrating multi-tool things when I messed up and didn’t want to tear it all apart. I also only worked in 2×4 sections of plywood, commonly called handy panels.
The first panel is cut into 6 strips.
- 4 * 36×4
- 1 35.5 x 4
- 1 35.5x whatever is left, it will be under 4.
The 36 inch pieces are the two outside edges of the case and the two interior edges of the case. The 35.5×4 piece is the back side of the case, closest to the hatch and the 35.5 x whatever piece is for the front of the case closest to the back seat.
A hump exists near the back seats where the 3rd row seating would attach that needs to be accounted for. I cut a 4 inch x 1.5 inch notch about 8 inches back from the front of the case to go over the hump. Later I would go back and cut that a little more to fit a solid board that would allow me to use factory bolt holes to attach the box to the floorpan.
With the basic frame sorted it was time to mount the interior edges. I chose to do a roughly 17 inch cavity on one side and a 15 inch cavity on the other. With the spacing decided, I next created a contoured floor up near the seats that allows me some shallow storage where there would have otherwise been wasted space due to all of the curves and bumps in the floorpan.
I didn’t want to have to drill into the flooring so I’m using the factory tie down locations in the very front of the box. I did end up setting two 1/4-20 rivnuts into existing factory holes for the second mount and I’ll use the factory sliding tray mounts to hold the rear down. I also lined the area with sound deadening material because I can’t stand an interior that squeaks and creaks.
Next up was just mounting the doors. I used a single piece of 1/2 plywood 2 inches larger than the dimensions of the box itself. I mounted the piano hinges and the top together before I cut the doors, then I took a circular saw and cut a straight line where I wanted the doors to be split. Doing that guarantees a square fit and easy closing.
I didn’t get pictures of this part, but next I drilled 2 inch holes to fit some marine , flush mount slam latches to hold things tight with some flush mounted door magnets to help. With the latches and magnets mounted it was carpet and flooring time. My 4runner came with a rubber mat that was supposed to go over the carpet but always ended up sliding all over the place. It perfectly fit though under the box and gave a great surface for stuff to sit on. I used some cheap automotive carpet and permatex headliner spray to attach it all. a 3×3/4 trim piece makes the front nice and flush and hides the screws.
Everything I normally carry fits nicely inside with no rattles or squeaks to be had. I might fit some air struts at a later time, but for now I have a trunk in a 4runner 🙂
cyborgworkshop.org 
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