Category Archives: AWD

AWD, STi, Turbo, USDM, WRX

Rear Wheel Bearing Repair 02-07 Subaru WRX/STi

Rear Wheel Bearing Repair 02-07 Subaru WRX/STi: This is a write up on how to replace your rear wheel bearing for your 02-07 WRX STi.

DISCLAIMER: WORKING ON YOUR CAR IS DANGEROUS. IF YOU FEEL YOU CANNOT COMPLETE ANY OF THESE TASKS, DON’T DO IT, THESE PARTS HOLD YOUR SUSPENSION AND WEIGHT OF YOUR CAR. THIS IS A REFERENCE ONLY! do not attempt.

Tools:
– 32mm Socket (axle nut)
– 19mm, 17mm, 14mm (suspension, and brake parts)
– Needle nose
– Sockets, breaker bar
– Torque wrench
– Access to a press
– I used a 36mm to press the bearing
– 26-27 mm for the hub

Parts
– Check with your local Subaru dealer
– Or use online sites or vendors!

Parts I Used
– Rear Wheel bearing – #28016PA010
– Oil Seal #1 – #28015AA080
– Oil Seal #2 – #28015AA070
– Rear Axle nut – #28044AA001

Rear Wheel Bearing Install

– First you need to break the torque on your lug nuts
– Get your rear in the air and stable (your going to put some stress on some parts)
– Remove your wheel

Rear Wheel bearing: Remove your wheel and Locate your axle nut and “uncrimp” it.

Locate your axle nut and “uncrimp” it. After its uncrimped, make sure you have your parking brake on really well. Either break the torque on it and back it off so its hand tight accessible, or remove it all together.

– Locate your axle nut and “uncrimp” it
– After its uncrimped, make sure you have your parking brake on realy good.
– Either break the torque on it and back it off so its hand tight accessible, or remove it all together
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AWD, Stance, Subaru, Suspension, WRX

Spring Installation guide for Subaru WRX STi:

Spring Installation guide for Subaru WRX STi:

 

1.) Remove the rear seat.

Tools: 12mm socket. Socket extension helps.

There are two brackets at the front of the rear seat. Remove the bolts holding them in and pull out the lower seat cushion. There are three brackets holding the seat back in. Once the bolts are out you can lift the cushion off. There are brackets at the top that support the seat; make sure those clip in properly when you put it back in. Also pay attention to how the cushion fits through the seat belt.

2.) It is easiest to bust loose the 17mm strut top nuts while the car is on the ground. So that’s what we are doing here…

Once the seat is out you can get to the rear strut dust covers. You’ll want a couple of tools to get to these nuts since the access is pretty tight. A 12mm open gear wrench (pictured) is nice. Also, standard 12mm sockets in various depths will be helpful. Unless you have air tools that can fit on these, there is a lot of wrenching involved since you can only get a few degrees per turn on some of them. Strut cover removed. Note the “out” inscription, and make sure it faces “out” when you put it back on. Top of the strut showing the nut that needs to be loosened. You should be able to get on there with a 17mm deep socket and loosen it a few turns. Just bust it loose, do not remove it at this point!

This next part isn’t critical now, but you will need the info later.

In order to make sure the strut isn’t spinning in the shaft, you need to insert a 6mm hex/allen wrench
into the strut top, and hold that still while you turn the 17mm nut. This is the contraption I use.

Now to the front.

Remove the little rubber dust covers in the center of the top mounts. Again, bust the top nut loose. On the front passenger side there may be a bracket that holds an alarm chirper. It doesn’t really matter if you take the 12mm nuts off now or later, I am just including it at this point in the process. If you do loosen them now, again, make sure to keep them on at least a little bit so the struts don’t fall off later.

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AWD, STi, Subaru, Transmission, Turbo, USDM, WRX

Clutch replacement for a Subaru WRX/STi:

How to replace a Clutch for a GD Subaru:

This procedure was performed on a MY04 STi with some modifications which may or may not be relevant for the purposes of this How-To. This procedure is only ONE way of removing the transmission and is not meant to be the be-all method. This is a DIY on your driveway process only. If you have access to a lift, this would be the preferred and safest method.

Perform this procedure AT YOUR OWN RISK.

Clutch: This procedure allows you to remove the transmission from a Subaru STI for the purpose of gaining access to the clutch and flywheel system for inspection and or replacement

This procedure allows you to remove the transmission from a Subaru STI for the purpose of gaining access to the clutch and flywheel system for inspection and or replacement.

This procedure allows you to remove the transmission without the benefit of a lift and is meant as a DIY for the weekend warrior. This is by no means a simple or easy procedure and it requires a good deal of strength. IT IS RECOMMENDED YOU HAVE A FRIEND THERE TO HELP. You will need a second pair of hands at times.

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AWD, Ej20, EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

Flywheel: Flywheels for Subaru WRX/STi’s FAQ

Flywheel FAQ:

How does a lightweight flywheel improve performance? A transmission can be thought of as a fulcrum and lever in a car. First gear has a really long lever; second gear has a shorter lever, etc. The lever represents the mechanical advantage that gears give your vehicle. When your car is moving, you have two factors that are present during acceleration, one is driveline losses, which are constant and the variable, which is vehicle weight and the mechanical advantage supplied by each gear.

Flywheel: SPEC flywheels are CNC manufactured at an unheard-of .001 tolerance, in an industry where the standard is .010. This precision manufacturing process ensures perfect balance and a perfectly flat bedding surface for the clutch disc, both of which also contribute to the ultimate in safety for competitive environments. All SPEC flywheels carry SFI certification.

While changing to a lighter flywheel will give the user little to no changes on a dyno, the apparent changes are quite dramatic due to the greater mechanical advantage. Consider these made up figures for consideration: Drive line losses, 45 pounds and vehicle mass (weight) at the driveline (remember your gear’s mechanical advantage reduces your actual car weight). We know that within reason, vehicle mass is a constant.

Now imagine if you reduced the driveline loss from 45 to 35 with the use of a lightweight flywheel. Since the engine has less drivetrain losses to compensate for, this means the “gained” horsepower can be applied to moving the vehicle mass. Using mathematics, one can realize that the higher you go up in gears, the less effect that a lightened flywheel will have to the overall equation.

Are there any downsides to a lightweight flywheel? While the performance characteristics of a lightweight flywheel seem to be the perfect solution, there are compromises:
a. Low end performance is affected. This usually means that higher revs are necessary for smooth starts due to the reduced rotational mass. For drag racers, this can be a BIG issue.
b. Possible missfire check engine light.
c. Possible chatter, like missfire this affects some users and not others.

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AWD, Ej20, EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

Clutch: Subaru WRX/Sti clutch FAQ

Clutch: Subaru WRX/Sti clutch FAQ

The first impulse when clutch shopping is to get “too much” clutch. This is often a very big mistake, as there will be compromises in the different types and compositions of clutches.

Clutches hold Torque, not Horsepower:
Most performance enthusiasts relate more to horsepower numbers rather than torque, but clutch capacity is measured in terms of torque. Think in terms of a high rpm 250 HP Honda Civic versus a 250 HP Ford Powerstroke turbo diesel. The truck will need about three times the clutch capacity because the engine produces about three times the torque.

Choosing what’s best for you:
It may be difficult to know what clutch is right for a particular application since there are so many different levels of personal tolerance and many variations in design. Some people can tolerate clutch chatter, or noise, or heavy pedal effort, or shorter clutch life, higher cost, or other trade-offs. But why tolerate unnecessary issues if you don’t have to? Get the clutch that suits your needs.

What are the various clutch materials? Other than unique or specialized compositions, clutches are generally comprised of:

1. Organic
2. Kevlar
3. Ceramic
4. Feramic
5. Carbon (initially invented in 1998 by Alcon Components for the Subaru World Rally team )
6. Sintered Iron

Depending on manufacturer specifications, this list also shows the general order of the amount of force the clutch materials can hold.

Organic: Metal-fiber woven into “organic” (actually CF aramid with other materials), original-equipment style. Known for smooth engagement, long life, broad operating temperature, minimal-to-no break in period. Will take hard use, somewhat intolerant of repeated abuse (will overheat). Will return to almost full operational condition if overheated. Material is dark brown or black with visible metal fibers.

Kevlar: High-durability material more resistant to hard use. Engagement is similar to organic, but may glaze slightly in stop and go traffic, resulting in slippage until worn clean when used hard again. Higher temp range in general, but can be ruined from overheating; will not return to original characteristics if “cooked”. Material is uniform yellow/green and may look slightly fuzzy when new.

Ceramic: Very high temperature material. Engagement is more abrupt. Will wear flywheel surface faster, especially in traffic situations. Due to it’s intrinsic properties, ceramic has a very high temperature range. Material is any of several light hues – gray, pink, brown.

Feramic: This unique clutch material is one that incorporates graphite and cindered iron. The result is a friction material that offers good friction coefficient, torque capacity, and smoothness of engagement.

Carbon: Very high temperature material. Engagement is more abrupt. Will wear flywheel surface faster, especially in traffic situations. Slightly more durable and flywheel-friendly compared to other aggressive clutch materials. Material is black.

Sintered Iron: Extremely high temperature material. Engagement is extremely harsh and is generally considered an “on/off switch” both due to it’s characteristics and the clutch types this material is generally associated with. It requires a special flywheel surface. Material is metallic gray in color.

 

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AWD, Ej20, ej20G, Intake, Intercooler, JDM, Legacy, Rally, Subaru, TMIC, Tuning, Turbo, UK, wrc

Legacy: 1989-1994 Subaru Legacy (BC/BF) GT/RS

Prior to the Legacy RS turbo, Subaru had never enjoyed the experience of distributing a genuine performance car. Of course, there had been the 4WD turbo RX and Vortex, but neither could crack 10 seconds for the 0-100km/h sprint – although they were very reliable. The RS was the gun version of the first Legacy series released in 1988 and discontinued in 1994. The RS (Rally Sport) model was aimed squarely at world rallying, with many of its components and concepts carried over to the dominating Impreza WRX.

Legacy: The BC/BF is unique in having an Air – Water intercooler with a front mounted radiator for optimal cooling. The bonnet scoop only provides cooling to the turbo. While later model legacy’s have all used air to air intercoolers.

The center Viscous LSD on the MT models initially starts out with a 50/50 torque split, front and rear, and will up the ratio towards the end with more traction. The manufacturer doesn’t give a final figure, so the max split is either 65/35, or could even venture as high as 95/5, since the A/T model has a different system that is marketed at a 65/35 maximum split. A higher ratio would explain some of the handling characteristics at the limit. The rear differential is also a Viscous LSD model.

The BC/BF is unique in having an Air – Water intercooler with a front mounted radiator for optimal cooling. The bonnet scoop only provides cooling to the turbo. While later model legacy’s have all used air to air intercoolers.

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AWD, Ej20, EJ25, EJ257, Intake, Intercooler, STi, Subaru, Turbo, USDM, WRX

FMIC (Front Mount Intercooler) STi/WRX FAQ

FMIC: The primary purpose of a FMIC (front mount intercooler) is to reduce post turbo air temperature prior to entering the combustion chamber via the throttle body.

FMIC install in a Subaru WRX STi.

HP gain is around 15HP. This figure can vary as results can be further enhanced with post installation tuning. This is one modification that is extremely difficult to put a traditional HP figure on as results truly vary from car to car based on tuning and turbo output in terms of CFM.

Which manufacturer is best? This topic is highly debated. There have been no reported consistent “bad” FMICs on the market. Obviously, there may have been bad FMICs sold, but not enough to report as “bad” overall.

Which FMIC construction method is best? FMICs have two main construction methods:
1. tube and fin
2. bar and plate
There is much debate as to which construction method is best. There are many pros and cons with each design type, but no real hard data. Bar and plate designs are consistently reported as more damage resistant which gives them the edge with regard to appearance longevity. In the end, you are best advised to chose a FMIC based on other qualities rather than concentrate on construction design.

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AWD, DCCD, EJ257, STi, Subaru, Tuning, Turbo, USDM, WRX

Transmission: STi 6-Speed basic swap info into a WRX

Front Differentials:
02-07 WRX: open
04 STi: “SureTrac” LSD
05-07 STi: “Helical” LSD

Transmission: Sti 6-Speed vs. WRX 5-speed

Rear Differentials: R160, R180
These were originally used in the Datsun 510, 610 and other IRS Datsuns. The “R” stands for Fuji Heavy Industries. The R180 was used in the front axle of Datsun 4×4 trucks (720, etc). The number represents the ring gear size in millimeters.

R160 – 52lbs. WRX rear differential. It has a viscous LSD which is no better than an open differential since the unit is so tiny in this differential.
02-05 have a 3.54 gear ratio
06-07 have a 3.70 gear ratio
R160’s on 2.2L Legacy/Impreza’s have a 3.9 gear ratio

R180 – 64lbs. STi rear differential. It has a mechanical clutch type LSD.
04-05 R180’s have a 3.90 gear ratio
06-07 R180’s have a 3.54 gear ratio

Center Differentials:
02-07 WRX: Viscous coupling type
02-05 has a 1.1:1 gear ratio
06-07 has a 1:1 gear ratio
04-07 STi: DCCD (Driver Controlled Center Differential)
04-05 has a 1:1 gear ratio
06-07 has a 1.1:1 gear ratio

Do I need different front axles?
02-early 04 WRXs have female axles and need to use stubs that go inside the transmission . Late 04-07 WRXs use male ended axles that slide inside the front differential so there is no need for stubs. For the female axles, you need axle stubs, circlips, and seals to reuse the WRX axles (check out the seal differences link for part numbers). You can use the stubs from your 5MT. For the male ended axles, they just slide right into place with the correct seals and circlips. 04 STi front axles will work too.

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