Building a Plywood Deck Plate in the Back of your JKU

[SBSYNCRO]

I posted this in the Wrangler forums because I received a lot of questions from folks on how I put this together. In case there are some folks here that don't frequent the JK section in Wranglerforum.com I figured I'd post it here too.
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If you're looking for a way to clean up the rear cargo deck of your JKU a plywood deck is a great way to do it. For about $50 in materials you can build one yourself that won't look quite as good as a Goose Gear system, but will be 100% useful and will save you about $500.




(pictures taken before painting to show it better)

This first phase addresses the area BEHIND the rear seats. I plan a Phase II that will delete the rear seats and replace them with another deck that is flush with this section, creating a continuous flat cargo deck much like the Goose Gear system.

Design considerations:

Its a bit tricky to figure out exactly how you want to design the system and you have a couple of options (I spent an entire weekend pulling apart the interior, measuring things, mocking up drawings, and just staring at the space). The rear floor of the Jeep is NOT even - there are two "humps" that stand about 1/2" to 5/8" proud of the main cargo deck. These are the "slots" that the rear bin lid slide into. Unless you want to take a sledge hammer to these and knock them down, you have to build off this height.

There are a lot of "layers" to contend with:
1. Jeep Logo mat
2. Carpeted Storage bin lid (or subwoofer cover) and its hinge slots
3. Carpeting
4. Plastic trim on both sides that also comes down to the horizontal plane and extends into the floor area


OPTION 1: Remove everything
With this option, you remove the black plastic trim pieces on both sides of the rear cargo area, and then also remove the carpeting for the rear area. At first I considered doing this, but once I had removed everything I just couldn't get comfortable with the exposed wiring looms on both sides of the body tub. I also didn't like the way the roll bar just jutted up out of the wheel wells.

OPTION 2:Remove only the Jeep logo cargo mat
This is the way I decided to go, though it does end up a bit uneven (I'll address that below). Using some rough measurements off the carpeted "floor" I determined that the horizontal portions of the two plastic trim pieces are roughly the same height as the two "humps" that the storage bin/subwoofer cover fit into.


Materials Required:

• Large sheets of cardboard - enough to create a 44" x 37" piece (if not use duct tape to create a large enough piece)
• 1/2 Sheet (4x4) of desired grade of plywood in either 1/2" or 5/8" thickness (I used 5/8" ACX which uses a waterproof glue). If you want to go "all out" and have a really good lumber yard nearby, you might be able to find Baltic Birch plywood in 5/8" thickness, but it will be expensive. It holds screws REALLY well, and is perhaps a bit more stiff than ACX.
• (4) M6 x 60mm button head screws, stainless or black oxide finish
• (4) 1" x 1/4" fender washers in the same finish as the screws
• (4) M6 x 40 studs (optional)

Tools Required:

• measuring tape
• Torx T30 bit and driver (for removing 4 cargo tie-downs)
• Large size contour gauge that will extend at least 4.5" and is as long as possible (min 10"). https://smile.amazon.com/AlexBasic-E.../dp/B07R6692TT
• Box knife with sharp blade(s)
• Large carpenter's square
• Sharpie pen
• 4mm allen wrench (for installing the new screws)
• Skilsaw or table saw (optional)
• Jig saw
• Palm sander with 80 and 150 grit paper
• Drill and 1/4" bit
• small piece of scrap of the plywood you're using, or something else that is about 3" x 3" of the same thickness

Method:

1. Remove Jeep Logo cargo mat (if you have one)
2. There are 3 cargo tie-downs on each side. Using Torx T30 bit, remove the 2 on each side closest to the front of the Jeep, leaving the rear two in place (the ones that are closest to the tailgate.
3. Take your piece of cardboard and make sure it is square with measurements of 43-5/8" x 36-7/8". Measure the 1/2 way point and fold it exactly in half along the center (approx 22"). Unfold
4. Using your contour gauge, measure the contour immediately behind the rear seats where it "necks in" toward the center. Transfer the contour to the cardboard template, then measure the distance down (or push the cardboard into place and mark it) and measure the contour of the second indent, which is a bit more complex because the plastic juts out a bit.
   
   
   
   
5. When you are done transferring the contours from one side of the Jeep to your sheet of cardboard with the Sharpie, cut and test fit that side.
6. Adjust as necessary. If you mess up, you can just cut away a patch and then replace with a larger patch using duct tape, then try again. SPEND AS MUCH TIME AS NECESSARY TO GET THIS RIGHT! (I spent two hours on this stage and 30 minutes on the rest of the project!).
7. Once you have one side fitting well, fold your cardboard in half and transfer your markings to the other side and trim to your lines. Unfold and test fit, making adjustments as necessary. It will take a bit of tweaking to get it right.
8. Now check the fit against the rear door using the 3 x 3 piece of scrap - you'll notice that because of the thickness, it may have more or less interference - trim away the area on the driver's side where the tailgate door bulges out, using your piece of scrap as a guide.
9. Once you have your template to your satisfaction, lay out your plywood and draw your cut line.
10. Use the skilsaw (or table saw) to cut off the two obvious areas of excess so that you end up with two large scrap pieces
11. Now use the jig saw to follow your cut lines, remembering to account for the thickness of your lines, and the thickness that gets added by transferring from a pattern.
12. Test fit the piece and make adjustments if necessary, making sure the back door clears the rear of the deck with enough space to allow for flex of the Jeep and any possible expansion of the deck.
13. If you have M6 studs, thread them into the four holes in the tub of the jeep from where the cargo tie-downs were so that they stand up about 1/2" above the floor of the Jeep. If you don't have studs, just thread your button head screws into the holes.
14. Lay the plywood deck over the studs or screws, making sure it is lined up the way it will be when installed. Tap the four places above the screws hard enough to transfer an imprint from the studs/screws to the wood.
15. Remove the deck and using the 1/4" drill bit, drill four holes where you transferred the imprints.
16. Paint/prep the deck as you see fit. I just hit it quickly with some 80 grit to round the edges and smooth the contours a bit, then went over everything with 150 grit. Then I hit it with a coat of satin black Krylon Fusion paint. I may hit it with Herculiner one of these days, or I might cover it with a rubber mat - haven't decided yet.

Now comes a decision point - are you a perfectionist? If yes, read this section, if no, skip to the next section

 

[SBSYNCRO]

PERFECTIONISTS

1. One of the problems I mentioned before is that the floor of the Jeep is not flat. There are differing heights across the cargo area. If you place your plate in at this point and screw it down, the plate will be supported only by the areas circled in red below:
   
   
   
   
2. If you're OK with that, then go ahead and skip to the next section. If not, you'll need some 1/4" plywood and some 3/8" plywood to address the areas highlighted in the photo. Using the same methods described above for measuring and cutting using the contour gage and a cardboard template, make two templates for the two areas. Then using the templates, make two additional spacers using the 1/4" and 3/8" plywood. Test fit with all three plywood sections to make sure everything feels solid and lines up.
3. I recommend drilling a 1" hole using a spade bit or hole saw where the forward screws will be installed in the 3/8" thick spacer. This will give you extra space so you're not trying to perfectly line up two sets of 1/4" screw holes.
4. Test fit everything again to make sure you can easily line everything up, but this time, drive some 1/2" brads or wire nails (tiny little cabinet nails) about 1/2 way into the tops of the spacers so that they stick up about 1/4" out of the top of the pieces. This is to create a pattern for gluing.
5. Lay down both spacers and then the top deck, lining up the holes and then install the screws loosely.
6. Once you're sure its lined up tap the top deck with a mallet or soft hammer so it pushes into the nails sticking up from the spacers.
7. Carefully remove everything - it should stay together as a single assembly.
8. Flip the work piece upside down (all three pieces stuck together) and draw lines around the spacers, then carefully remove them by prying them apart.
9. Glue and clamp the pieces back together using your nail holes and lines as guides.
10. Paint and prep the pieces according to your preference.
11. Continue to next step

NON-PERFECTIONISTS

1. Lay the piece back into the rear of the jeep and then using a small flashlight shined UNDER the plywood to line up the holes one at a time and insert the screws and snug "finger tight" using the 4mm allen wrench.
2. If you are following the "Perfectionist" method, you can snug the screws down good and snug (like with a 1/4" drive ratchet and allen head bit). If you're following the non-Perfectionist method, snug the screws down, but do not over-tighten - you will crush the plastic and bow the wood.

 

[dstock]

Nice write up! I did something similar but I chose to remove the the cargo cover and replace the full plastic cargo tray with the 1/4 version that covers the jack area but still allows access to the jack. I used a piece of 1 x 2 underneath for support which helps level everything out. You can see it in this photo before it got covered in carpet as well, along with the 1/4 cargo tray from a 2015-on model.

 

[SBSYNCRO]

How do you access the jack? Is the rear portion hinged to lift up?

 

[dstock]

The plastic cargo/jack cover just lifts straight out, it's not the full size cargo tray. It looks like this:

 

[SBSYNCRO]

Ah! Didn't know such a thing existed- did you just cut yours or do different years/models have a different two-piece design? One thing I don't like about this project is how much space gets wasted underneath. - I opted to go all the way to the rear door in order to optimize the deck area, but I'm toying with some ideas to create a lift-out panel

 

[dstock]

I believe this comes with the models that have the subwoofer installed in the floor. I found it on Ebay and it was called "15-18 Jeep Wrangler JK With 9 Speaker Alpine System Rear Cargo Tray Mopar New" You could of course just cut yours to work as well I would imagine.

I hear you on the wasted space. I may still cut a door into mine as well to access the cargo area similar to what Goose Gear does with their baseplate. The reality is when we are on a trip you'd still have to remove stuff to get to access. Always tradeoffs!

 

[SBSYNCRO]

PHASE II - Removing the rear seats

I'll post a full write-up on the project when I get some time, but here's a follow-up to this thread. I finally finished the last touches on the deck this weekend (well, still waiting on the hinges and cam locks to arrive from McMaster-Carr for the cubbies).

My plan is to install a fridge slide on the Driver's side for a Dometic CFX50 (still trying to decide which one is most space-efficient) and then wherever it falls on that rear cubby door, I will split the door and hinge it, screwing down the left side with removable machine screws (into threaded inserts), but leaving a small hatch that is accessible with the fridge installed. The rear seat area is accessible when the doors are open so that I can stow a couple of shotguns in soft bags under there on hunting trips.

At some point, I will probably need to drill out the M6 rivnuts in the body tub that hold down the back piece and replace them with something a lot more stout, but for now, everything lines up perfectly and is very solid - no rattles or squeaks on the street. We'll see how she does over washboard in Baja....



Fabricated brackets installed into the former seat mounting holes. Note the M6 rivnuts on the horizontal portion - this is what secures this forward section of the deck.
https://imageshack.com/i/pl0w6zKbj

 

[SBSYNCRO]

and regarding some of my earlier posts about how to get things to fit over the rear area and the various clearances involved, I ended up removing ALL the "stuff" (carpet, hatch cover, plastic tub) and adding layers to the rear plate to take up the space and make it sit flush. Here is a shot of the rear plate section from the underside:




The forward edge of the rear plate rests on top of a section of the front plate (which must be installed first) and they are bolted down together to the body tub. Here you can see the "tail" of the front section where the rear plate mates up:




And here is some detail of the rear section, which is layers of 5/8" plywood, with a final piece of 1/4" ply to cover the access hole for the scissor jack. I think I'm abandoning that storage space for now - I can't come up with a good way to make a removable section for just that.

 

[caspice]

@SBSYNCRO
Thank you for providing the write-ups and photos. Always nice to see other methods. You have inspired me to redo my own modest platform.

 

[harpersJK]

Very nice write up! What did you use to glue the rubber flooring down with?

 

[SBSYNCRO]

Very nice write up! What did you use to glue the rubber flooring down with?

I used a combination of double sided carpet seam tape and 3M spray adhesive. Messy, but it seemed to work well so far. Tough to do without getting some voids/bubbles, but it stays tacky long enough that I could pull it up and redo if necessarily


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[harpersJK]

I used a combination of double sided carpet seam tape and 3M spray adhesive. Messy, but it seemed to work well so far. Tough to do without getting some voids/bubbles, but it stays tacky long enough that I could pull it up and redo if necessarily


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Thanks, working on my platform as we speak!

 

[SBSYNCRO]

The carpet seam tape is good along the edges where you want really strong adhesion.


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[reaper229]

Nice job,clean and functional
What is your diamond style black on the floor?
Did the same diy platform 2 years ago on my jku 07 and i put some anti-slippery carpet but i hate it,mud and dust are hard to clean.I need to find something else.

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