If you’ve been following along with my C10 Cheyenne upgrades, then you know I’m in the process of building a cool street truck that can hold its own at any cruise night, and be a reliable daily driver. In my opinion, I have the appearance upgrades handled and now it’s time to focus on some performance enhancements. This month, my update is accomplished with the help of Moser Engineering.
From the factory, the Cheyenne was equipped with an anemic 350ci engine, Turbo 350 transmission, and a 12-bolt rearend with 2.76 gears. While the combination does offer great drivability on the highway, there isn’t much fun to be had when traveling from red light to red light. Knowing the immediate effect a gear swap can offer, I decided to start by doing something with the rearend of the truck as the first step to my performance goal. Sure, a gear swap can definitely deliver huge grins while driving around town, but go too steep with gear selection (numerically high), and highway cruising will needlessly suffer. I need the Cheyenne to have the best of both worlds, so moderation is the order of the day.
Just A Little Steeper
To that end, I gave serious thought to a set of 3.73 gears for the upgrade. While some might question the choice as being a little “steep,” I feel the choice will make a nice compromise for fun around town. But, I know what you’re thinking — those gears might not be the best choice for highway driving with the Turbo 350. You are correct. But, those gears will be a great match-up with the planned overdrive transmission upgrade when it is completed.
Our 12-bolt housings are completely new and manufactured from Moser-owned casting boxes – Jeff Anderson, Moser Engineering
Having a complete plan outlined before any parts are ordered is a great idea. At first, I thought about rebuilding the factory rearend. But, when I priced the new differential (gotta have a posi), bearings, gears, seals, gaskets, and axles, I learned a complete Moser Muscle Pak rearend was definitely a viable option.
That being said, if I were to rebuild the factory rear, I “could” reuse the housing, axles, and drum brakes. But, I plan to add disc brakes to the truck eventually, so in actuality, the housing and the axles would be the only thing I would keep. There is a peace of mind in knowing the Moser unit is all new.
The Moser built-to-order 12-bolt Muscle Pak is a complete unit ready to slide under almost any vehicle, and getting a new casting seems like a no-brainer. “Our 12-bolt housings are completely new and manufactured from Moser-owned casting boxes,” says Jeff Anderson, Moser’s marketing director. “Moser only uses U.S.-made steel, forged in U.S. plants, using Moser-designed dies and tooling. You feel the sense of devotion to the U.S. and patriotic pride when you talk to the people at Moser.” In fact, the company’s founder, Greg Moser, used a team of engineers to develop the proprietary material that the company still uses today.
A Complete Package
When you are ready to order a Muscle Pak rear, you’ll find Moser offers a wide range of gear ratios, axles, differentials, and even several wheel-stud options. Also, although I chose to include an Eaton posi in my build, other options include; Detroit Locker TrueTrac, WAVETRAC (35-spline only), Auburn differential, or a spool.
Brakes are another consideration I needed to… well… consider. While the factory drum brakes did technically work, adding a set of rear discs was something I planned to do in the future anyway, so why not order them now. Disc-brake options come in the form of economy units, Wilwood binders, or Moser-spec drag-race parts. If you wish to stick with drum brakes, that is also an option. You can even opt-out of ordering brakes entirely. In my case, this isn’t a race truck, so the economy binders were chosen.
The economy disc brake kit is in fact, designed around ’79 through ‘84 Cadillac Eldorado calipers. These calipers incorporate an emergency brake, which is a must-have in my opinion. The E-brake on these calipers does require the brakes to be bled in a certain sequence, or you will never get the air out of the system.
In short, the E-brake must be adjusted before any fluid is introduced into the caliper. If they are adjusted with fluid in them, it forces an air pocket into the piston of the caliper. This is because the piston is further back in the housing than the bleeder. All I can say is follow the instructions. If you decide to forego the reading part, there is a process involved to remedy the spongy pedal feel you will get for doing things incorrectly. It’s also a lot messier to fix once brake fluid has been introduced.
It seems axles are usually the first thing in a rearend that seems to break. Muscle Pak axles come in a variety of spline counts, and the choice is yours. You can also utilize the OE-style C-clip retaining method or the recommended “bolt-in” retainer that eliminates the axle C-clip. Moser’s technical crew recommend the bolt-in axles, because of the additional safety factor the parts deliver. (i.e. if you break an axle, you won’t lose your wheel.)
“Our development team has tested the bolt-in axle retainer with most types of brakes and brake backing plates to ensure there are no fitment issues. A T-bolt kit for axle mounting comes with the built-to-order package,” Jeff affirms.
When it comes to connecting the rear to your driveshaft, fitment options continue to abound. There are multiple pinion-yokes available. Most GM cars and trucks use a 1310-series yoke. But, if you want to add a little strength — and I did — a 1350-series is available. If you want a really trick piece, Moser even offers a 1350-series yoke in billet aluminum.
For a standard upgrade on a vehicle that isn’t destined for track use and launching on slicks with huge horsepower, the 1310 yoke is sufficient and should fit the OE driveshaft without a problem. “If you’re throwing a lot of horsepower at the rearend and have tires with serious grip, you might want to consider the 1350-series yoke,” Jeff states.
Finally, you have even more options when choosing the rearend finish. The standard option delivers an unpainted rearend for those wanting to save a few pennies and paint the housing themselves. But, several powdercoating colors are available as well. The Moser Muscle Pak I spec’d for my truck was ordered in a matte-black finish. In actuality, I like the look of the matte housing with the silver-hued bolts showing.
Out With The Old…
As you can imagine, swapping the rear is a really straightforward process. In an afternoon, the Cheyenne received a bullet-proof Moser rearend that I couldn’t wait to test out, and test I did. I don’t have to tell you that swapping from a 2.76 to a 3.73 rearend gear definitely makes the truck a blast to drive around town. In fact, I might even get myself into some trouble. Although engine RPM is understandably higher than before (2,800 rpm at 60 mph), tire smoke now comes much easier when leaving from a dead stop. AS expected, the transmission also shifts through the gears much sooner than before. But, that’s to be expected, as the engine RPM climb much quicker than before.
But, the real benefit of the gear swap will be realized when the TCI-built 700R4 is finally stabbed into place. That’s when I will be able to fully enjoy the benefits of both the steeper gears when leaving from a dead stop and the pleasure of being able to cruise the highway with the help of the overdrive transmission. There is no doubt in my mind the truck will be a blast, I guarantee it.