Subaru Performance Transmission Improvements
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There's probably a transmission shop in almost each and every city within the country that may develop a bulletproof transmission for American made cars. Whether it is a late model Mustang or a 60's Chevelle, there are lots of aftermarket elements and several years of technology available for the transmission rebuilder to make use of.
The same cannot be said for your 4EAT automatic transmissions found in Subaru vehicles. In factory form, these transmissions show a number of problem areas that can cause failure in as little as 20,000 miles with a stock engine and even sooner in revised applications.
Poor shift quality, anemic factory components, and most importantly, incorrectly configured torque converters plague the automatic transmission equipped vehicle. This is in conjunction with the automatic's propensity to burn out the high clutch pack (third gear) and also the 2-4 clutches (2nd and 4th gear) with even moderate boosts in engine output.
Recognizing the necessity to take import and sport compact automatics to their fullest potential, IPT Performance Transmissions- a new Jersey based company, dedicated a large percentage of their research time and money towards improving the Subaru automatic transmission.
First up on the hit parade of internal improvements is the need to address the issue of valve body calibration. The valve body mods are really the basis of any performance trans rebuild. An automatic transmission utilizes a network of valves, servos, solenoids, orifices, accumulators and passages that control and route hydraulic pressure to the appropriate places to use the clutches and bands.
Without entering elaborate details which might fall outside the scope of this short article, suffice it to say that modifying the valve body successfully changes the speed of clutch apply and also increases the clamping force with which these elements have to work with. This is why shift kits and altered valve bodies produce that firm, performance type shift that boosts the transmission's general capacity for power handling.
Next, all crucial support bushings need to be replaced to make sure that the centerline of the transmission goes in perfect alignment with the centerline of the crankshaft. Disregarding this step places lots of unnecessary stress on the internal transmission parts.
Many of the various other parts also like the pinion shaft, the front differential ring gear and the planetary gearset endure several metallurgical processes like heat treating, Meta-Lax stress relieving, and cryogenic treatment (freezing them in liquid nitrogen at -300 degrees Fahrenheit to 'reset' the part's structure on the molecular level).
Lastly, all of the required seals and gaskets are changed to materials that are better able to cope with the heat and stress that's common in high powered applications. Performance clutches and steel reaction plates are mounted and their clearances set to a lot more accurate specifications than those that are used by the factory. Most importantly, IPT utilizes a proprietary 6 disk high clutch pack along with a 5 disk 2-4 clutch pack which increases the 2nd, third, and fourth gear torque capacity by over 25% versus the factory set up- this is the key to acquiring a high powered vehicle make a 1-2, 2-3, and 3-4 shift instead of just bouncing off the rev limiter.
As for the alterations outside the gearbox, the next thing of importance is of course the torque converter. In an automatic equipped car, one of probably the most essential components in the entire car in regards to optimizing performance is a correctly configured converter.
Additionally to being made with many strength improvements over the factory piece, a performance converter enables a car to better make use of the RPM range at which optimum power is made. In simple terms, a correctly created converter will allow a vehicle to start under more power by enhancing the rpm at which the launch takes place. Essentially, a torque converter is a definitely variable transmission in and of itself, and altering its torque multiplying characteristics becomes completely necessary when other variables in the vehicle are changed (bigger turbos and bigger cams).
Even in otherwise stock turbocharged Subaru cars, ET reductions of more than one full second aren't in any way unusual with the addition of a correctly configured converter.
Transmission, torque converter and valve body upgrades aren't only for American made cars any longer. Improved performance, durability and much more effective shifting is now available for your vehicles of nearly every manufacturer- thanks in part to the couple of companies that are willing to do the research and advancement work required for this rapidly growing part of the automotive aftermarket.
For more details, please follow this link: http://www.importperformancetrans.com/subaruauto.shtml
-John Lombardo, IPT Performance Transmissions
Article Source: Articlelogy.com
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