Skidplates protect a variety of components on a truck’s underbody, including the radiator, steering system, oil pan, transfer case, exhaust pipes, and more. There’s an important application for a diesel GM HD pickup in particular: shielding the diesel exhaust fluid (DEF) tank. On ’11-and-later Chevy and GMC pickups, it’s mounted fairly low on the passenger-side framerail, and vulnerable to damage.
If most of your job sites are on the street, this exposed mounting might not be a problem (unless you have to climb over a steep curb or a log). But on rough terrain, this lack of ground clearance can result in damage. For example, we spoke with a company that provides mechanical lube services to mining outfits in Northern Nevada, which reported more than a dozen tanks getting punctured or even scraped off while driving on rocky access roads.
If the DEF tank does get punctured, the engine computer can sense a lack of DEF and go into shut-down mode, leaving you stranded in a remote area. Besides an expensive tow bill, replacing the tank is pricey as well, and patching it is not really an option. A new tank costs about $1,000, and installation time takes at least a couple of hours (or more, depending on any other related damage).
Although GM now includes a thin skidplate on later-model trucks, shielding the tank with heavy-gauge steel plate is cheap insurance, especially if you head off-road or visit gnarly work areas on a regular basis. While there are a few different designs available for the aftermarket, the ’11-and up DEF Tank Skidplate shown here is from T&A Performance ($599 in bare metal, plus shipping). Made from 3/16-inch hot-rolled steel, it’s secured with five, ¾-inch, Grade 8 bolts threaded into stainless steel sleeves that are welded to the underside of the passenger-side framerail.
| T&A Performance’s skidplate comes in bare metal, welded out of 3/16-inch steel plate. Here it’s shown with a matching silver finish from Fine Line Powder Coating. Included are Grade 8 bolts with threaded stainless-steel inserts.
This extra step of welded mounts located inboard is critical, because there’s no solid attachment possible on the outboard side (since there’s just thin sheetmetal there). With this setup, “It can handle a floor jack lifting up a pickup, even with two wheels raised off the ground,” notes Tim Anderson of T&A Performance.
Although fairly straightforward in concept, fitting this skidplate in place requires some careful preparation and test-fitting before applying either paint or powdercoating to the bare metal. To drill holes for the threaded inserts, T&A Performance recommends using a Blair Holcutter kit (#14006), instead of a conventional hole saw. Note that the framerail rises upward at the forward end, so two of the collars for the threaded insert sleeves are angled and need to be extended slightly to stay on an even level with the others.
Prior to welding in the inserts, grind off the undercoating on the frame, exposing bare metal. Also, Anderson recommends the batteries be disconnected to prevent the welding machine from accidentally frying the engine computer.
Since the skidplate comes unpainted, do any slight modifications (such as enlarging the mounting holes) before applying paint (Dupli-Color Bed Armor coating is a scuff-resistant coating). For a spiffier style, Fine Line Powder Coating applied a silver finish that matches the color of truck, giving it the look of a factory upgrade.
More importantly, the T&A Performance DEF tank skidplate not only covers up that funky-looking plastic tank, but it also provides a tough shield that’ll keep you from getting stranded and hit with an expensive repair bill.
