Diesel World - - Tech -

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.

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