General Motors used a wide array of manual transmissions in its vehicles over the years, but the four-speed gearboxes from Muncie and Borg-Warner are undoubtedly the most popular. The Muncie four-speeds have a distinct reputation for strength and durability, but the second-design T10 developed by Borg-Warner in the ’70s, which is often referred to as the Super T10, is nearly as durable as any regular-production Muncie. It was the OE transmission in many Pontiacs from mid-year ’74 up into the ’80s. The sheer number of Super T10s produced during that era, and the fact that they are still produced today, makes used examples an affordable option for virtually any project.

So how can you improve the performance and reliability of your Pontiac’s Super T10? Follow along as we provide a number of ideas to help accomplish exactly that, and you might be surprised to find that not all are in the transmission!

1) High Quality Rebuild Kit

There are a number of manual transmission rebuild kits available today, and the quality of the components they include can range from very poor to very good. While price is generally indicative of the overall quality of a particular kit, knowing exactly what it contains is equally important.

A basic kit will include main-case bearings, gaskets, and seals. A better kit may also include new captured roller bearings, needle bearings, brass synchronizer rings, and snap rings and washers. The most complete kit might include such components as the cluster gear shaft, synchronizer keys and springs, and a case-extension bushing. Beware of inferior kits that are on the market, however. Not all of those available today include OEM-quality components.

You should purchase your Super T10 rebuild kit from a reputable transmission rebuilder or transmission-parts supply store. As opposed to simply ordering a kit online, it may be worthwhile to speak with a company technician to determine what your particular transmission may need. The overall condition of the Super T10 you’re rebuilding will determine exactly what’s required, but a quality kit with the right pieces will go a long way toward keeping your four-speed operating reliably for many years to come.

2) New High-Quality Gears

The gears of Borg-Warner’s regular production Super T10 were constructed of 8620-alloy steel—an affordable material that is quite durable. As gear ratios increased, so did the number of teeth on the main and cluster gears, and that reduced the maximum torque capacity of the entire transmission.

Not so coincidentally, the Super T10 that Pontiac specified for its high-torque 400 and 455s was a close-ratio unit with a First-gear ratio of 2.43:1, which happens to boast of the greatest torque capacity rating of any Super T10. While complete gear failure of a 2.43:1 transmission in a stock-type application is relatively uncommon, there’s no telling just how much abuse a particular transmission has been subjected to over the years.

If any gear looks as if it isn’t worth reusing, it may be best to opt for a new stock-replacement rather than take chances reusing a questionable original. Readily available from most any transmission rebuilder or transmission-parts supply store, the money spent on one or several new gears is relatively cheap when you consider that any such failure will require complete transmission disassembly, and, quite possibly, a long list of new parts.

3) Cast-Iron Bearing Support

The Muncie and Borg-Warner four-speeds were comprised of a main-case, bearing-support, and case-extension. As its name implies, the bearing-support is a cast plate that houses the large roller bearing, which supports the entire main shaft, and the bearing is retained by a snap ring on either end. Located between the main case and extension, the bearing-support is often called a mid-plate.

On production transmissions, the bearing-support was constructed of cast-aluminum, and the material proved rigid enough to endure the forward and rearward thrust that the main shaft sees during normal operation. The hard and quick shifts a manual transmission sees in high-performance applications can take its toll on the bearing-support, however, and that can distort the bearing flange, or even cause it to fatigue and crack, in extreme cases.