Improving a 2012 LML Duramax

After a few months hiatus, Project LML is back for its final installment of the build. Over the last year and a half, this 2012 Silverado made quite the transformation, with everything from suspension and chassis improvements to horsepower upgrades under the hood. When the project was introduced in the March 2018 issue of Diesel World, the plan was to take a completely stock, higher-mileage LML Duramax and turn it into the ultimate daily driver with the versatility to tow whatever you needed, drive where ever you wanted, and do it all with unmatched performance and reliability.

This month, it was time to focus on a few upgrades that had been skipped through the build but are still items any GM owner should contemplate when perfecting the longevity and overall reliability of a truck. Early on in the build we installed a Stage 3 leveling kit system from Kryptonite Products that included upper control arms, leveling keys, ball joints, and new Bilstein shocks. While all of that helped raise the truck up and kept proper CV angles and ball joint angles, we overlooked some key steering upgrades. With the addition of some heavier wheels and tires, we added some strain on the front end and knew the factory tie rods wouldn’t appreciate it if we ever had to use the four-wheel drive system. The GM independent front suspension has been notorious for bending or breaking tie rods in off-road situations or in sled pull/drag race competitions that require planting a bunch of power through the front tires. To prevent an issue that might leave us looking for a tow, the stock tie rods were replaced with the massive Kryptonite Death Grip Tie Rod package. The Death Grip tie rods use chromoly nickel heat-treated outer studs and steel inner-ball sockets for unmatched durability. The massive hexagon-shaped bodies are super strong and make it easy to install and adjust for proper alignment. Kryptonite also prides themselves with their USA-made products and lifetime warranty, meaning these will be the last set of tie rods you ever buy.

While the 2011-’16 Duramax has a decent-sized transmission cooler stuffed behind the bumper, in heavy towing situations in the heat of the summer, there is an advantage to a larger cooler with increased surface area and better placement for increased airflow across the core. The new Mishimoto trans cooler was designed to be the answer to every Allison’s excessive heating problems.

Previously, Project LML had also seen some cooling system improvements, with the addition of Mishimoto’s replacement intercooler and radiator upgrades. When we replaced the factory Allison transmission with a fully built unit from Merchant Automotive, we also replaced the factory trans cooler with the high-flow unit from Mishimoto, but we ran out of space in that issue of Diesel World to highlight it. So, circling back around to that install, you’ll see the obvious reasons to making that upgrade happen. Anytime a new transmission is installed, it’s always recommended to do a full system flush of the cooler lines and cooler, or possibly even replace them depending on the condition of the factory transmission. The last thing you want when a brand new transmission is installed is for leftover debris from the failed unit to find its way through the system.

The 2011+ GM trucks came with some new styling on the front end. Most distinguish them by this larger hole in the center of the bumper compared to the 2008-’10 model trucks. The larger hole was designed to increase airflow to the transmission cooler tucked back there, but obviously it leaves a bit to be desired.

Just recently, Mishimoto engineers developed an easy-to-install and effective transmission cooler upgrade for the 2011+ LML Duramax trucks, and we were lucky enough to get one of the firsts for this build. The new cooler system dwarfs the stock unit and mounts in a much more sensible location with easy-to-install brackets. While the factory cooler resides behind an opening in the bumper, the Mishimoto unit is placed directly behind the grill in front of the cooling stack, where it can receive more airflow to help keep trans temps down. In our towing tests with the new cooler installed, it dropped a consistent 25-30 degrees off our fluid temperatures, which was huge when towing long, slow grades in the summer. The new trans will be much happier about life not running at 220+ degrees under load.

This install was a super-easy task and took less than an hour. It was even completed without making a giant mess spilling fluid. To start the job, the upper plastic shield must be removed, which uses a handful of push pins to locate it.

For the last part of the build, we needed to do something about storage. This truck is used on a daily basis to haul kids around and commute to work. On the weekends, it’ll tug a 30-ft fifth wheel to the mountains. Under the seat was stashed an assortment of things like a first-aid kit, jumper cables, tie down straps, spare clothes, and more. Sure, the truck had room for everything, but having it slide out from under the seat or rolling around in back got old. It was time to fix the storage situation. After some searching, we ordered up one of the new lockable under-seat storage boxes from Tuffy Products.

With the upper cover and the grille assembly removed, you’ll have easy access to the factory transmission cooler lines and the mounting locations for the stock transmission cooler.

The 16-gauge steel box is form fitted and includes easy-to-install, no-drill brackets to give you the perfect place to secure whatever you need in the cab of the truck. The pry-guard locking system helps keep valuables safe when you’re away, and the design won’t interfere with the seats. The dual-hinged lid offers easy access from either side without having to raise both seat bases, and the optional foam inserts can be trimmed to safely hold any specific items you’re regularly hauling around. Plus, should the floor space be needed, the whole box can be removed in a few minutes without tools.

The factory lines use a simple, quick-connect fitting that will require a small, slide-pin clip hidden under the black plastic cover to be removed.

Dialing in Project LML has been a fun process and hopefully has been a good window for readers into how vast the aftermarket is for these trucks. With a little planning and the right list of parts, any truck can be transformed into the perfect tool for the owner.  This truck made 597 hp on the chassis dyno but is still great for towing heavy when we need it. We haven’t had to sacrifice drivability or usefulness as a daily driver. We’ve been able to adjust the stance and put on some more aggressive wheels and tires without affecting the ride quality. Most importantly, virtually everything we’ve bolted on to the truck should help extend the life of this truck.

The passenger side cooler line is just like the other side except for the 90-degree fitting that’s crimped onto the end of the hard line.
The small retainer clips that keep the lines locked tight into the fitting can be slid out of place and set aside. Don’t break or lose these—they will be reused.
Once the lines were disconnected, there were just four bolts that had to be removed, and the factory cooler was lifted out of place and laid in a container to drain out. Sitting next to the new Mishimoto cooler, you can see how much wider and taller the new unit is. The additional surface area in the cooler will help dissipate heat easier and should produce a consistent 20-30-degree temperature drop in fluid temps.
The kit includes a couple of mounting brackets, machined aluminum blocks, and factory-style, quick-disconnect fittings that will be installed so the factory transmission lines can be reused and plug into factory locations even though the cooler location will be moved.
The cooler itself will be mounted using suppled brackets that will bolt into factory holes in the core support bracket. The new location for the bigger cooler will allow much more airflow through the cooler, offering even better cooling. The kit includes two short lengths of hose used to connect the cooler to the supplied brackets installed on the previous step.
On the front end of every GM 2500HD and 3500 truck you’ll find a set of extremely undersized tie rods prone to bending and failure anytime a truck is used off-road or in a situation that requires four-wheel drive. The GM independent front suspension is notorious for ‘toeing in’ when load from 4WD is added to the front axles. Snapped or bent tie rods have left many owners stranded and looking for a tow.
Replacing the tie rods with a beefed-up aftermarket set is a no brainer when it comes time for replacement because of higher mileage or as a preventative step from getting stuck somewhere. This is also an install most anyone can do, but you’ll need to have a professional alignment done ASAP.
The Kryptonite-branded tie rods from are some of the best on the market and will dwarf the factory tie rod. The larger rod will hold up to much more abuse because the aftermarket rod ends are improved for longevity and reliability. They’ll be the last set you ever buy.
Just a tip: once the factory tie rod is removed, you can use a tape measure to check its length. Use that spec to adjust the length of the new tie rod to hopefully get your alignment close enough so that the drive to the alignment shop won’t be a sketchy, steering-wheel fight down the road.
With this roomy backseat area in the crew cab trucks, you’ve got all sorts of storage under the seat, but having stuff rolling around and sliding out from underneath at every stop can get old. Tuffy Products offers an easy-to-install lockbox to take better advantage of the storage space.
Using simple brackets that attach with the factory, rear-seat mounting studs, the nut can be removed, the bracket slid over the stud, and the nut replaced and tightened back down.
Once bolted into place, the Tuffy security box is the perfect place to store whatever you need to store.
The dual-lid design makes it easy to access either side of the box without having both seat bases raised. Tuffy also offer custom foam pieces that can be cut to fit whatever items you’d like to store.

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