2004 GMC Sierra Buildup - G2 Gear & Axle Master Overhaul Kit

As a grown man, I can't explain it, but the sound and smell of a burnout makes me smile. It's a phenomenon we're sure you can relate to. With that said, nothing is worse than trying to do a burnout, only to suffer the "one-wheel-peel" shame. Most 1/2-ton trucks leave the assembly plant with an open differential sending power only to the passenger-side rear wheel and tire. If you're lucky, or if you checked off the options box at the dealer, your truck may have a posi or locking differential and your truck benefits from sure-footed traction. If not, don't sweat it because this month's installment of our Project Novakane '04 GMC Sierra buildup is for you.

To get our Sierra to hook up while at the track, dragstrip, and in poor weather conditions, we contacted 4Wheel Parts and ordered a complete rear differential overhaul. Every part we replaced, we did so with an upgrade in performance in mind. These upgrades included: a new Eaton Detroit Truetrac limited slip, 3.73 gears (from the factory 3.42 gears) and master overhaul kit from G2 Axle & Gear, Mag-Hytec aluminum differential cover for our 10-bolt, and high-performance 75-90W gear oil from Royal Purple. Rather than cut any corners on the install, we went to one of SoCal's leading differential companies, Unitrax, in Anaheim, California. These guys have been giving cars and trucks better traction for 25 years, and they know axles inside and out. Whereas the install does require a press for installing the pinion and differential bearings, once that hurdle is overcome, you can do this install in your own driveway. If your truck could use improved traction and performance, this upgrade is a must.

We arrived at Unitrax, in Anaheim, California, in our '04 GMC Sierra equipped with a factory open differential and 3.42 gears. Thankfully, Unitrax will have our Project Novakane smoking rear tires in no time.
We arrived at Unitrax, in Anaheim, California, in our '04 GMC Sierra equipped with a facto
Step one was a simple but messy one. Each 13mm bolt was removed and the fluid drained by prying the factory diff cover from the rearend.
Step one was a simple but messy one. Each 13mm bolt was removed and the fluid drained by p
With the ring-and-pinion exposed, it looked pretty good for nearly 150,000 miles...

...but a closer inspection of the magnet in the diff cover showed a large buildup of fine metal shavings from excessive wear.
...but a closer inspection of the magnet in the diff cover showed a large buildup of fine
Moving to the front of the differential, an 11mm wrench was used to loosen and remove the driveshaft bolts. Note: A yellow marker was used to show the driveshaft and pinion positioning.
Moving to the front of the differential, an 11mm wrench was used to loosen and remove the
A 10mm wrench was then used to bust loose the axle clip pin bolt.

With the bolt out, then pin was slid out, and the axle C-clips removed with a pair of pliers.
With the bolt out, then pin was slid out, and the axle C-clips removed with a pair of plie
With the brake calipers and rotors removed, the axles could then be slid out from the axle tubes.
With the brake calipers and rotors removed, the axles could then be slid out from the axle
An impact was used to bust loose the differential bearing cap bolts. With the bolts loosened, the caps could be removed.
An impact was used to bust loose the differential bearing cap bolts. With the bolts loosen

After a not-so-gentle pull with a prybar, the factory differential was pulled free as one unit.
After a not-so-gentle pull with a prybar, the factory differential was pulled free as one
Once the large pinion nut was loosened and removed from the front of the differential, the factory pinion was removed.
Once the large pinion nut was loosened and removed from the front of the differential, the
Here is the new ring-and-pinion from G2 Axle & Gear. We opted for a 3.73 ratio and thanks to the forged 8620 gear steel construction, it'll hold up to excess loads of high-performance driving. Cue the burnouts please.
Here is the new ring-and-pinion from G2 Axle & Gear. We opted for a 3.73 ratio and thanks