2001 GMC Sierra ext. cab, two 12's, underseat, sealed, fiberglass, down fire

[tank313]

Finally getting around to posting the experience I had with my build. Anyone who has a early 2000's GM extended cab knows an under seat box that will fit a decent set of 12's is hard to come by. Most have very shallow mounting depths and are around 0.5 cuft. So I decided to build my self two sealed down fire enclosures out of fiberglass to maximize the space and let the subs actually breathe! The goal was to get 1 cubic foot per sub and at least 3 inches of clearance from the floor without modifying the rear seat configuration. Here's how it went...

Click to read more...

 

[wew lad 5,000+ posts]

looks like it went well

 

[tank313]

I started by molding the floor which would end up being the feet and cutout where the sub goes (down firing). I found out that although a plastic sheet releases the fiberglass well, it doesn't contour to the floor as well. So I switched and used foil. The ripples in the foil stick to the resin but it was worth the tight mold.

 

[tank313]

Next I had to frame up the walls to fill the space from the floor to the seat. I used dowels and hot glue to come up from the floor and stretched nylon across the frame to create the wall shape. The nylon was coated with resin and then layered with fiberglass.

The excess fiberglass from the floor mold was then trimmed. After this step all that was left to seal the box was the lid

 

[tank313]

The rear seat has a lot of loose fabric under the seat and I wanted to utilize this space. The challenge is that the seat frame has a bend at the outer edges that needed to be molded. To do this I used floral foam and shaped it to fit by taken off material little by little and test fitting as I went.

The final shape was then covered with duct tape and molded with glass. Once dry the mold was released, cut to shape and attached to the rest of the box.

 

[tank313]

When I had a completely sealed box I cut out the bottom to fit the subwoofer. It was important to allow a gap from the sub to the body so I taped a spacer to the bottom of the sub attached it to the mdf mount and placed it in the cut out.

I used small strips of fiberglass at the corners to attach the mdf to the rest of the box while the sub was in place and allowed these strips to cure. I could then pull the sub out with the mdf staying in place and go crazy attaching the mdf to the box without the sub in the way.

 

[tank313]

With everything attached came the fun part...First sanding the glass to knock down all of the raised edges.

Next the low spots were filled with bondo and then sanded, and then filled with bondo and then sanded and then filled with bondo and then sanded...This went on forever.

Once the surface was smooth it was painted.

 

[tank313]

Result...

 

[tank313]

The results were amazing! I ended up using an SCV-2000 to power the two FI SSD 12's and I couldn't have been happier. Six months later the engine in the truck needed to be rebuilt and I decided to buy a new truck rather than fix it. It was fun while it lasted but now I am selling everything from this build to do something with the new truck. It was a lot of work that had a short lived reward but it was still worth it, I learned a lot about building a custom box and fiber glassing. It was something I always wanted to do with that truck and finally got around to doing! Worth the experience!!!

 

[wew lad 5,000+ posts]

looks pretty awesome, surprised you sold the truck you can go buy a new LS motor for cheap

 

[tank313]

looks pretty awesome, surprised you sold the truck you can go buy a new LS motor for cheap

It was hard to part ways but I wanted the 4 doors and diesel motor. The funny part is, I never would have thought I would have less room under the seat with the 4 door...if it's easy it's not fun right?

 

[wew lad 5,000+ posts]

It was hard to part ways but I wanted the 4 doors and diesel motor. The funny part is, I never would have thought I would have less room under the seat with the 4 door...if it's easy it's not fun right?

yeah you really cant beat a 4 door duramax with the allison so i dont blame ya