| There is probably a transmission shop in almost every | | | | gearset undergo various metallurgical processes such |
| town in the country that can build a bulletproof | | | | as heat treating, Meta-Lax stress relieving, and |
| transmission for American made vehicles. Whether it is | | | | cryogenic treatment (freezing them in liquid nitrogen at |
| a late model Mustang or a 60's Chevelle, there are lots | | | | -300 degrees Fahrenheit to 'reset' the part's structure |
| of aftermarket components and many years of | | | | on the molecular level). |
| technology available for the transmission rebuilder to | | | | Lastly, all of the required seals and gaskets are |
| utilize. | | | | changed to materials that are better able to cope with |
| The same cannot be said for the 4EAT automatic | | | | the heat and stress that is common in high powered |
| transmissions found in Subaru vehicles. In factory form, | | | | applications. Performance clutches and steel reaction |
| these transmissions demonstrate several problem | | | | plates are installed and their clearances set to much |
| areas that can cause failure in as little as 20,000 miles | | | | more exacting specifications than those that are used |
| with a stock engine and even sooner in modified | | | | by the factory. Most importantly, IPT utilizes a |
| applications. | | | | proprietary six disk high clutch pack and a five disk 2-4 |
| Poor shift quality, anemic factory components, and | | | | clutch pack which increases the second, third, and |
| above all, improperly configured torque converters | | | | fourth gear torque capacity by over 25% versus the |
| plague the automatic transmission equipped vehicle. | | | | factory set up- this is the key to getting a high |
| This is in conjunction with the automatic's propensity to | | | | powered vehicle make a 1-2, 2-3, and 3-4 shift instead |
| burn out the high clutch pack (third gear) and the 2-4 | | | | of just bouncing off the rev limiter. |
| clutches (second and fourth gear) with even moderate | | | | As for the modifications outside of the gearbox, the |
| increases in engine output. | | | | next thing of importance is of course the torque |
| Realizing the need to take import and sport compact | | | | converter. In an automatic equipped vehicle, one of the |
| automatics to their fullest potential, IPT Performance | | | | most important components in the entire car in regards |
| Transmissions- a New Jersey based company, | | | | to optimizing performance is a correctly configured |
| committed a large portion of their research time and | | | | converter. |
| dollars toward improving the Subaru automatic | | | | In addition to being made with many strength |
| transmission. | | | | improvements over the factory piece, a performance |
| First up on the hit parade of internal modifications is the | | | | converter enables a vehicle to better take advantage |
| need to address the issue of valve body calibration. | | | | of the RPM range at which maximum power is made. |
| The valve body mods are really the foundation of any | | | | In simple terms, a properly designed converter will allow |
| performance trans rebuild. An automatic transmission | | | | a vehicle to launch under more power by increasing |
| utilizes a network of valves, servos, solenoids, orifices, | | | | the rpm at which the launch takes place. In essence, a |
| accumulators and passages that control and route | | | | torque converter is an infinitely variable transmission in |
| hydraulic pressure to the appropriate places to apply | | | | and of itself, and altering its torque multiplying |
| the clutches and bands. | | | | characteristics becomes absolutely necessary when |
| Without going into elaborate detail which would fall | | | | other variables in the vehicle are changed (bigger |
| outside the scope of this article, suffice it to say that | | | | turbos and bigger cams). |
| modifying the valve body effectively changes the rate | | | | Even in otherwise stock turbocharged Subaru vehicles, |
| of clutch apply and also increases the clamping force | | | | ET reductions of over one full second are not at all |
| with which these components have to work with. This | | | | uncommon with the addition of a properly configured |
| is why shift kits and modified valve bodies produce | | | | converter. |
| that firm, performance type shift that increases the | | | | Transmission, torque converter and valve body |
| transmission's overall capacity for power handling. | | | | upgrades are not only for American made vehicles |
| Next, all critical support bushings need to be replaced | | | | anymore. Increased performance, durability and more |
| to insure that the centerline of the transmission runs in | | | | efficient shifting is now available for the vehicles of |
| perfect alignment with the centerline of the crankshaft. | | | | almost every manufacturer- thanks in part to the few |
| Ignoring this step puts a lot of undue stress on the | | | | companies that are willing to do the research and |
| internal transmission components. | | | | development work required for this rapidly growing |
| Many of the other parts also such as the pinion shaft, | | | | segment of the automotive aftermarket. |
| the front differential ring gear and the planetary | | | | |