A vehicle’s rear axle shafts might possibly be the last components considered when improving the performance and reliability of any Pontiac. Though complete failure of a stock shaft is rather uncommon in a street car, in the event that it ever occurs, it often leads to significant collateral damage to the drivetrain and body.
Axle upgrades are always recommended whenever racing regularly. As our street-driven Pontiacs approach or exceed 40 years old, and with many amassing 100,000 miles or more over their lifetimes, a simple axle upgrade is a worthwhile consideration, especially if a larger displacement engine with greater output and/or wider tires with improved grip are in the foreseeable future.
Moser Engineering in Portland, Indiana, has developed an affordable solution that provides greater-than-stock strength in a package that fits and installs just like an original. Its stock-replacement Street Axles are ideal for high performance applications or when looking for a suitable replacement for a worn original. Follow along as we install a pair of Moser Engineering Street Axles in our ’76 T/A, and have it back on the road in less than two hours.
In ’71 Pontiac began using in its Firebird a new differential that contained an 8.5-inch diameter ring gear fastened to the carrier using 10 large bolts. This “8.5-inch, 10-bolt,” as it’s commonly called, was built by Chevrolet and uses axle shafts that measure 301⁄16-inches long and contain 28-spline carrier ends. The axle shaft is supported by a large roller bearing pressed into the axle tube on one end, and a C-shaped retaining clip on the opposite end.
Over the years the 8.5-inch 10-bolt axle has proven very durable. It can withstand significant amounts of power without failure. The axle shafts and bearings in our ’76 Firebird hadn’t ever presented problems, but with future power increases quite likely, we decided it was time to replace the originals, which are now more than 35 years old. We wanted something that fit without modification but was more durable than stock, and Moser Engineering was sure to have an answer.
Moser’s Street Axles are exactly what we needed. They are CNC-machined from forged 1541HM material that’s induction heat-treated. That, along with specific design enhancements, produce an axle that’s 30 percent stronger than stock. The Street Axle replaces an original without any modifications, and also accepts stock-replacement knurled wheel studs that must be pressed on, or is threaded to accept longer-than-stock studs required for certain racing classes.
The Street Axle is ideal for applications ranging from stock-replacement to high-performance use. Moser is quick to point out that imposing a horsepower limit for its axles is difficult because much depends upon engine torque, vehicle weight, and just how hard the axles are loaded upon initial takeoff. If you plan on racing regularly, the company recommends following the guidelines imposed by racing organizations, such as NHRA, which requires some type of axle retention device (often called a C-clip eliminator) for cars running the quarter mile quicker than 11 seconds.
Part number A102803 is the correct Street Axle for any ’71-’81 Firebird fitted with drum brakes. (If your ’78-’81 Firebird is equipped with a J65 disc-brake rear axle, Moser can accommodate it, and also offers 12-bolt applications for ’701⁄2 Birds.) Retailing for $260 per pair, we ordered a set and opted to have Moser install the wheel studs for $18 and followed its recommendation of using new bearings and seals, adding $30 to the total. The entire package was on our doorstep within days.
The install was very straightforward, as you will see in the photos and captions. While there’s certainly nothing wrong with reusing original axles if they remain in excellent condition, Moser Engineering’s Street Axle line is an excellent choice if you’re looking for an upgrade that’s stronger than stock, installs quickly and easily, and is affordable.
