General Information 4EATstands for Four-Speed Electronic Automatic Transmission. This simplymeans that your vehicle is equipped with an automatic transmission withfour gears. The gears for the 4EAT are as follows: Automatic transmission gear ratios for 2.5RS: 1st - 3.027 2nd - 1.619 3rd - 1.000 4th - 0.694 Reverse - 2.272 Final drive ratio - 4.44 Each gear can be taken tothe following MPH 1st-38 2nd-71 3rd-112 The4EAT is also equipped with the VTD (Variable Torque Distribution) AWDsystem. This AWD system adjusts power to wheels depending on drivingconditions, making it more technically advanced than the AWD systemused in manual-equipped vehicles. The normal driving split is 45% tothe front wheels and 55% to the rear wheels. How does the 4EAT differfrom the 5MT? Is it better or worse for performance? Thefirst difference between the 4EAT and 5MT is the AWD system. 5MT modelsuse a permanent 50/50 split between the front and rear wheels, whereasmodels equipped with the automatic make use of the technically superiorVTD system (mentioned above). The second difference is the gearing. The4EAT uses 4 gears to make use of its power, where 5MT models make useof 5 gears. Froma stop: The 4EAT (stock) is much different performance-wise than the5MT. Models equipped with the 5MT are able to achieve theirpavement-rippling sub-six second 0-60 and low 14 second ¼ mile timesthanks to its ability to launch at 4000+ RPM. Models equipped with the4EAT must use the brake-torque technique (I also take no responsibilityfor potential damage caused to your car using this technique), however,stock 4EATs using this method can only launch at a maximum 3200 RPM,leading to a 0-60 time in the low 7 second range and a ¼ mile in themid-to-high 15 second range. Froma roll: Judging from the very few 4EAT vs 5MT races that I havestudied, a 5MT will have about a 2 car lead on a similarly equipped4EAT in a race from 40 MPH to 100 MPH. Please note that in the fewdocumented races known, the 4EAT begins to trail after it shifts to 3rdgear, leading me to believe that the 4EAT’s major weakness are it’sgear ratios. Stock5MT models dyno at around 170 WHP where 4EAT models dyno at around 150WHP. From my research, I have noticed about a 20-25 WHP differencebetween similarly equipped 4EAT and 5MT WRX’s due to the extradriveline loss through the torque converter. What you need to make the4EAT comparable to a 5MT in acceleration and ¼ mile times. Youneed a high stall torque converter. The main purpose of this mod is toraise the stall speed from 3200 RPM to around the 4200 RPM range;allowing the 4EAT to run 0-60 and quarter mile times consistent with5MT equipped vehicles. This mod is a MUST HAVE if youare planning on consistently drag racing your vehicle. The use of thismod for owners whom do not consistently drag race is debatable. Someargue that it increases daily drivability; others argue that it doesnot. You’ll have to decide. I am not interested in 0-60or ¼ mile times, how else can I make my 4EAT a better daily driver? Althoughthis is highly subjective, the general consensus is that the bestmethod to increase your 4EAT’s drivability is by installing anaftermarket header, uppipe and turbo back exhaust system . This willvirtually eliminate turbo-lag and give much better low and mid-rangepower. You can also add engine management to take full advantage ofyour modifications to further increase responsiveness and decrease lag. Best First Mod for the 4EAT Althoughthe idea of the best first mod is highly subjective, I, along with manyothers, feel that an aftermarket exhaust system is the best firstmodification for the money. This modification greatly decreasesturbo-lag, causing the car to perform better in all circumstances. Best New Turbo for the 4EAT Wehave found that a GT30R is the best turbo replacement for the 4EAT.Both the VF 34 and 39 have decent spool-up, with good mid-range and topend. If you plan on doing short block upgrades and running higher than18 psi, then we have found the GT30R to the our favorite. Ofcourse, you will also need the necessary supporting mods to run a newturbo. A great deal of research must be done if you decide that a newturbo upgrade is right for you. Using a Blow-Off Valve on a4EAT Yes,it can be done, but the difference between using a BOV on a 4EAT isthat you will not hear much of the “pssshhh” sound when thetransmission shifts. This is because the 4EAT holds its boost duringshifts. I heard that thetransmission in the Auto can hold more power than the transmission thatis used in the manual. Is this true? Yes,this is true up to a point. The general consensus is that the 4EAT is astronger transmission than the 5MT and will last a very long time aslong as it is properly maintained and the abuse is kept to the minimum.The 4EAT is an extremely hard transmission to “break,” but it is unableto cope with too much extra power because its shifts are still tunedfor stock levels. Once you begin to cross to cross the 250 WHP barrier,you need to consider “beefing up” your transmission with a performancetorque converter and valve body upgrade. This need increases if youplan on launching your vehicle or driving it hard on a consistentbasis. Very few people have actually broken the 'teeth' of the 4EAT,and with a full internal transmission upgrade, the 4EAT will handleover 800WHP. Can I manually shift the transmission ala Manumatic? Althoughavailable as a true manumatic in Japan, the American version of theautomatic WRX does not contain that feature. You may manually selectthe gears, although there is little purpose as A) manually shiftingfrom a stop will not net you better acceleration and B) it does putextra stress on your transmission. I manually shift the automatic froma stop frequently and through the gears without any issues. However,the manual functionality of the 4EAT can be useful for proper powerdelivery when cornering, it can also be used to place the car in abetter gear when racing from a roll. 4EAT Idiosyncrasies Theautomatic in the WRX is a lot different than any other automatic that Ihave driven. The 5MT guys can choose the gear that they want their carto be in, keeping the car in it’s optimal power band. We can do that aswell, it just takes knowing how to fully use the automatic to takeadvantage of the car’s power band. Lets review the different gearselections on the automatic gear shifter. (please note that thefollowing information is intended towards stock vehicles. The rules arecompletely different for modded or even lightly modded cars). 1:This is a special situation gear (explained further in the manual) Itshould be used rarely, if never. Some owners like to start out in 1 to‘manually shift” the gears. Please note that the transmission will notautomatically upshift while in 1, so when you shift into the next gear,make sure to do so at least 1000 RPMs early because of the shiftingdelay. 2:This is also a special situation gear (explained further in yourmanual). Starting off in 2 will start your car in 2nd gear, not first,making it perfect for dyno tuning, but doesn’t make much sense fordaily driving. Please note that the transmission will not automaticallyupshift, so make sure to shift at least 1000 RPM early because of theshifting delay. 3rdgear is sometimes referred to in other cars as “D.” By selecting 3, thecar will drive normally but will not upshift into 4. Selecting 3 isideal when you are driving in any situation where you will not bemaintaining a constant speed (while driving in the city, for example,or climbing a steep grade). By selecting 3, your car will also be muchmore willing to downshift into 2 when extra power is required, making 3the Power Gear of the WRX. Interestingly enough, there have been somereports of a .2 second better time at the track thanks to the moreaggressive torque split while in 3. Dis sometimes referred to in other cars as “OD.” By selecting D, the carwill drive normally and shift into 4th gear as soon as it can. This isonly ideal while maintaining a constant speed (Highway, freewaydriving). While in D, the car does not like to downshift into 2nd gear,making it a poor gear selection for times when quick passing responseis necessary. Why the 4EAT is betterthen the 5MT. Allof us are forgetting the main advantage of the Auto-WRX: the AWD systemitself. When we talk of 'Rally Proven', the 'proof' is actually missingin the Manual-WRX. Here is the reason why: TheVTD-AWD system of the Auto-WRX is the most advanced AWD system ofSubaru, with a true torsen (torque sensing) planetary gear centerdifferential, which works in association with electronically controlledcontinuously variable multi-plate clutch-packs. The torque split is at45/55, with a slight rear bias in power, in normal driving, unless moreis needed front or back. This system equals in sophistication andeffectiveness, the best AWD systems currently available in the marketincluding the Audi Quattro (not the 'Quattro' present in the Audi TT,which is inferior to the VTD-AWD). The VTD-AWD system is conceptuallyidentical to the AWD systems present in the World Rally ConqueringSubarus, the significant difference being that the WRC cars have driveradjustable torque splits and are much more of a heavy-duty kind. Thehardware otherwise is identical in design. The Rally Subarus also havea true auto-manual transmission, which is actually a clutch-lessmanual, but the underlying AWD system is better adaptable to theAuto-WRX, not the manual-WRX, due to which the manual-WRX soldiers onwith an AWD system that is essentially tractor-technology. 'Gets thejob done' but nothing to write home about. The other Auto-Subarus do not have thetorque-sensing center differential and drive more like a FWD car innormal driving. Themanual WRX on the other hand, has the same Viscous coupling AWD systempresent in all other manual Subarus, which is a reactive system, asopposed to the proactive nature of the VTD-AWD system of the Auto-WRX.The viscous fluid which is used to transfer torque front/back needsslippage before it can react and transfer torque. Also, sincedifferential lock is achieved due to the viscous fluid being twisted(unlike the torque sensing incredibly sturdy planetary geardifferential in the Auto-WRX), the torque-transfer is both slow and inefficient. The AWD system of the manual WRX cannot be compared with theAudi Quattro or any other sophisticated AWD system. It does not havethe breadth of operation (cannot transfer the amount of torquefront/back like the VTD-AWD), the reactiveness (reacts slowly due toits very Viscous coupling nature) or the rapid torque transfercharacteristics (due to the 'reactive' nature of the system) of theVTD-AWD equipped Auto-WRX. With the Viscous coupling AWD system presentin the manual-WRX, Subaru certainly would not be winning manyrallies....just a heads-up. Everythingelse remaining the same, I would have preferred a manual in the WRX.But in this particular case, everything else is not the same. Far fromit! Let’s face it - we love these cars for their AWD systems and notfor their 'manual gear shift capability'. 4EAT_Phase_II_Automatic_Transmission 4EAT Transmissions
So on that criteria, theManual-WRX has a huge and glaring deficit andthe 4EAT is the “BestKept Secret”. | 
