The rearward axle brackets will slip right into place on your factory axle U-bolt plates using all the factory hardware. The frame-side bracket will require holes drilled in the frame, which will be the most challenging part of this install. The double-walled boxed frame is tough to drill, but patience and a good drill bit goes a long way here. Since the boxed frame won’t allow a bolt to be installed easily, HSP supplies a nifty self-holding stud that will grab the frame from the inside when positioned correctly and allow the brackets to be bolted in place. The bars themselves use a rebuildable and greaseable upper joint for full range of motion, and the threaded attachment point allows the bars to be made longer or shorter by loosening the jam nut and rotating the heim one way or the other to change preload on the axle. After an initial test drive and a couple wide-open throttle runs, we quickly noticed how much better the transmission seemed to shift as the tires and axle stayed planted and offered a more positive feel through the drivetrain. When towing, we no longer feel that slight shudder when leaving a stoplight and we’re trying to apply all that torque to get the load moving and up to speed quickly. The traction bars made a noticeable difference in driving feel and the added fluid capacity should keep the rear differential and axles happier while towing through the 100+ degree summer days.
For the next parts of the build, we’re planning to remove the cab from the frame and swap in a whole bunch of
performance goodies to take this truck to an all new level of performance and drivability. We’ll also be looking into a full transmission build soon, since we’re positive the stock 124,000-mile Allison won’t endure 600+ horsepower for long. We also plan to do a few more cosmetic upgrades with some fender flares, maybe a front bumper and some new side steps. Stay tuned as we continue to take Project Looks. Muscle. Longevity from stock truck to the ultimate daily driver and weekend tow rig.
The newly installed HSP traction bars not only look great under the truck but serve a real purpose. We noticed almost instantly the improvement in the truck’s feel while towing. There is no longer shudder from the drivetrain upon leaving a stop and the tires stay planted regardless of throttle input.
Since we’re already doing a fluid change on the rear differential, it seemed the perfect time to replace the factory cover with something a little better. The cast aluminum cover from afe Power will allow an additional quart of oil and has been designed to help keep fluid temperatures down under heavy towing conditions. Plus, it looks great.
The axle has a built-in drain that makes servicing pretty simple by using just a 3/8” ratchet to remove the plug. Upon draining, it appeared this fluid was in decent condition as it didn’t show any signs of being burnt or neglected for the 125,000 miles on the odometer. The magnetic drain plug didn’t show much metal material either, which was a good sign.
The factory rear axle is an extremely tough piece of the drivetrain, but it’s often the most neglected part of the truck when it comes to maintenance. Not many think about how much heat and abuse the gear oil takes, especially when towing, and a rear end service is easily completed on the 2011+ trucks.
On this GM application, refilling the axle with fresh Synthetic 75W-90 gear oil is simple. The included fill port allows easy access to pour fluid in, and the sight glass on the side of the cover lets you know when it’s full. Our truck took exactly 5 quarts. Note the pre-drilled and tapped 1/8” port that could be used for a temperature sensor should you ever want to install one.
Using the supplied stainless Allen head bolts, the cover can be installed and snugged into place. The bolts need to be torqued to specs listed in the afe Power instruction manual. Be sure to torque in a star pattern around the differential to make sure the O-ring makes the proper seal without binding up.
The afe Power differential cover uses a simple O-ring supplied in the kit to seal the fluid inside instead of the factory-style paper gasket. This O-ring will offer a solid seal and make future axle repairs easier if the cover ever had to come back off for some reason.
With the OEM cover removed and sitting beside the new afe cover, you can see the difference in overall shape and casting. The new cover will hold a little extra fluid and help dissipate heat due to its finned design.
Before installing the new pan, the axle must first be thoroughly cleaned to remove any of the original pan’s gasket to ensure a clean, flat sealing surface. This is also a good time to inspect the ring gear for any abnormal wear marks.