If you’re looking to get the most drop in the rear of your truck without cutting a hole in the bed, this is the article for you. Lowboy Motorsports, in Mesa, Arizona, is now offering an underbed C-notch that can be shipped in pieces, ready to weld in by a local fabricator near you or in your own garage if you possess the skills to do so. However, not all truck frames are alike. Many newer pickups have bends, built-in mounts, or other hardware designed into the frame near where the rear end would center with a frame notch. The Lowboy crew has thought of all these factors, and they’ve designed templates for most applications through the years so they can prepare each piece before shipping the product to you.
In this article, we’ll show you what is necessary to get a full 6-inch drop in the rear of the ’18 Chevrolet Silverado. In this case, the owner was able to get 4 inches lower than factory with an aftermarket axle flip kit and shackle flip installed. After the notch was added, the original factory spring perches were put back in with the shackles positioned to the factory position. The notch installation and reworking of the aftermarket lowering kit allowed for a true 6-inch rear drop without any more slamming of the axle into the frame or bumpstops. Follow along as we show you how Lowboy Motorsports prepares the notch pieces for simplified installation on your year, make, and model pickup then welds one in on this ’18 Chevy.
| Before: Here's our ’18 Chevrolet Silverado with a 4-inch lowering kit. At this height, the rear of the truck is still higher than the front. The Lowboy Motorsports C-notch is needed to allow axle travel after the other changes to the rear suspension to make it a 6-inch rear drop.
| The truck was pulled up to the lift at Lowboy Motorsports, where the crew began removing the rear wheels, tailgate, bed bolts, and bed, making sure to unplug all electrical harnesses and the fuel filler neck. The gas tank was also removed prior to any work beginning.
| The pieces to the Lowboy notch kit vary by application, but this is the initial kit for the ’18 Chevy.
| Using a bend line that has already been pre-cut into the parts, the notch is shaped for each application before it is installed or shipped to the customer.
| Here is the kit after the top and bottom bends have been completed.
| The truck frame was then prepared for welding. This is a tedious process, as the factory coating and grime buildup can be hard to remove even with a sanding disc. Acetone was used to help scrub off the coating down to bare metal. The center line where the axle lines up was measured and drawn onto the frame for easy reference.
| The center line was then marked on the notch side piece, and the bend lines were drawn for each side. Here's where the Lowboy Motorsports notch differs from others on the market. The side piece is marked so that it can be bent to fit flush with the factory frame curve. Otherwise, there would be a large gap if a standard flat piece was used.
| The slight bends are made at the markings to make sure the product matches the factory frame angles.
| You can see the slight difference from this angle when they are laid on a flat surface.
| When clamped in place onto the frame, the piece now follows the factory frame angle change.
| The other side was matched up with its counterpart after being bent to fit in the same way as before. Other truck makes and models have minor differences in the preparation of the underbed notch, which is why templates are kept on hand so the product can be bent or cut to fit right on your truck.
| The sides were lined up, measured, clamped, and fully welded into place.
| On the ’18 Chevy, the center bed brace can be cut out to get the maximum possible space without cutting any of the bed floor out. Then the remaining edges were sanded down to remove any burrs or rough spots.
| Then the bed could then be painted or coated to cover the exposed bare metal.
| The top was test-fitted after a slight bend to line up with the side bends. You can see that the top and sides match up perfectly to allow maximum welding surface area between the separate pieces.
| With the top sides welded in, you can see here that the axle will have much more room to travel without contacting the frame.
| The rest of the top is welded together, filling each gap equally and consistently.
| Here is the finished top piece, which was examined carefully before the next step. Any issues could lead to stress cracking sometime in the future if the welding isn't complete.
| The factory frame section under the notch could now be cut out. Once removed, the surface area for the last notch section was visible all the way through.
| The bottom piece was lined up flush with the bottom of the side sections and welded into position.
| The undersides of the side pieces were also welded for full strength of the new section.
| The minor overhang of the notch sides could then be cut off. This extra section was left on the sides to allow for some adjustment and repositioning before any welding was started.
| Using a sanding flap disc, the notch is cleaned up and readied for paint, powdercoat, rubberized undercoating, or whatever you choose.
| Here's our finished Lowboy Motorsports underbed C-notch. When the coating is dry, the disassembly process is reversed to reinstall the gas tank, bed, and tailgate.
| After: With a few changes to the aftermarket drop kit on the truck and new shorter shocks, the rear sits 2 inches lower and the axle will no longer hit the frame with every bump in the road thanks to the underbed notch. Get in touch with Lowboy Motorsports to see what options are available for your truck.