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.
This basic Super T10 rebuild...
This basic Super T10 rebuild kit, which features high-quality components, was sourced from our local transmission-supply parts store. It retails for about $125 and includes everything necessary to rebuild a transmission that’s otherwise in good working order. (The included gaskets are not shown.)
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.
New OE-quality stock-replacement...
New OE-quality stock-replacement gears for the Super T10 are readily available from many sources, including your local transmission supply store. Not to be confused with the high-nickel 9310-steel gears produced for the Power Brute Super T10, which are no longer available, these stock replacements are constructed of 8620 steel, just like the originals. Expect to spend somewhere around $100 for each individual gear and about $200 for the cluster.
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.
Borg-Warner offered its Super...
Borg-Warner offered its Super T10 four-speed manual transmission with a number of different gear ratios, and the easiest way to identify them is by the number of machined grooves on the input shaft. Pontiac specified a close-ratio gearbox with a 2.43:1 First-gear ratio for its 400 and 455 engines, and it will have two rings on its input shaft.
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.
The bearing-support is sandwiched...
The bearing-support is sandwiched between the main case and the extension, and it’s often called a midplate. It houses the large roller bearing that supports the main shaft, and the constant jerking motion that occurs during hard shifts can compromise the integrity of the cast-aluminum original. Used originals like this are available, but S-K Speed in Lindenhurst, New York, offers an exact reproduction for less than $100.
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.
What happens when your attempt...
What happens when your attempt to channel too much power through a regular-production Super T10? The main case can flex, which prevents the gears from meshing properly, and that can lead to irreparable gear failure. Our modified 455 sheered two teeth from the cluster gear, and that damaged the opposing gears of the main shaft. We hoped to prevent this from happening again with some specific modifications.
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.