The 3-4-gear clutch pack is...
The 3-4-gear clutch pack is upgraded to nine friction and nine steel plates, (shown installed) along with the BTO-designed special spring kit (not shown), which results in a quicker 3-4 gear-clutch release.
Another BTO feature is that the one-year limited warranty doesn't start until the transmission is installed, and the pressure and temperature are checked and called in by the customer. Thus, if you're working on a project that becomes far more long-term than you intended (don't they all?), you won't burn up your transmission warranty while it sits on the floor of your garage.
Drive Report
Out on the road with the 2,600-stall converter, aggressive escapades with the throttle in First gear result in sideways, tire-boiling launches. Although this isn't the quickest way to the next stoplight, it does result in a toothy grin. It's less of a problem hitting Second gear; although the tires chirp hard, the GTA stays straight and hooks up again quickly. The Third gear shift gives a less dramatic chirp. By the time we approach Fourth, we're starting to wonder if the stock brakes are less adequate than we recall.
Around town, the 2,600-stall converter requires a tad more throttle and about 1,900 rpm to get the car moving from a standstill. It slips a bit more than the stocker when cruising normally until it locks up, and also softens the shifts at part throttle. Torque converter lockup is much more noticeable now: Engine rpm drops substantially-like going into Fifth gear-and a slip-free connection gives the Bird the feel of a manual transmission until tapping the brakes unlocks it.
Higher horsepower applications...
Higher horsepower applications often split the input drum around the input shaft splines. BTO makes a CNC-machined, steel brace (in hand, left) to press into the sun shell (right) to prevent this on Level 2 and up transmission builds.
Despite the same type of transmission with a higher-stall converter, we were surprised to find that on a 100-mile highway road trip, we actually showed a gain of about 1.6 mpg over the old iteration. This is probably the result of less internal drag from new bearings/bushings and, of course, the advantage of proper operation. The temperature gauge does run hot when we've been stuck in traffic on a 95-degree day, but it cools down quickly when we get moving and otherwise runs well within BTO's approved temperature range.
All in all, we learned a great deal about automatic transmissions and what makes them tick. Most importantly, we got our GTA back under its own power. We now have a great deal of confidence that whatever twist of fate puts our Pontiac on a tow truck again, it won't likely include the transmission as long as we maintain fresh fluid and keep the temperatures down.
Lockup For Vintage Vehicles
BTO will also install an automatic Fourth gear and manual-converter clutchlockup system in custom-order applications at no charge. Although we didn't need this system, it allows for automatic Fourth-gear torque-converter lockup older vehicles without a computer, requiring the optional BTO wiring harness (PN TCCRELAY700; $35) that uses the brakelight switch to unlock the converter. This system also allows the use of an optional dash-mounted manual switch to lock/ unlock the converter, which is useful for locking the converter in lower gears if the owner is towing uphill or just going for maximum gas mileage.
The strange-looking torque...
The strange-looking torque converter on the left is a small-diameter, 2,600-stall unit, built with a fullsize lockup clutch similar to the 2,000-rpm unit on the right. Although more expensive than a non-lockup converter, this design is the key to getting a great launch while retaining decent street manners. The lockup feature becomes increasingly effective to provide decent highway fuel efficiency and decrease harmful fluid overheating as converter stall speed increases.
Shown here is the new 29-element...
Shown here is the new 29-element input sprag (also called a roller clutch) going into our transmission. It's a clever design, resembling a gear with teeth that are retracted on springs. When the sprag spins up, centrifugal force forces the teeth outward so they can engage and thus drive the carrier, which in turn drives the clutch packs.
BTO supplies a pan with a...
BTO supplies a pan with a drain plug installed, so it's a simple swap to the fluid-temperature sensor that comes with the BTO transmission-temp gauge we added.
Gardner also recommended we...
Gardner also recommended we install the largest-possible transmission cooler and go with the radiator-style instead of the budget pipe-with-cooling-fins style. It should be mounted in front of the radiator where the fan will pass air through it.