Project Summary:

This installation will replace the factory clutch, with an option to also replace the factory flywheel. The pictures were taken from a 1999 Impreza 2.5RS coupe, but should also apply to any model Impreza.
There were absolutely no instructions whatsoever with the kits. This project is not recommended for the faint of heart nor for the mechanically-challenged. The instructions are geared towards those (like Edwin and I) who do not have access to a real garage with fancy equipment like lifts and engine hoists. The first installation was done on a quiet street.

New! If you didn't see it from the previous page, I have also documented an improved clutch replacement procedure.

Materials Required:

1 ACT Street clutch kit or equivalent (from Powerhouse Racing, iSR Performance, Teague's Auto), consisting of:

Pressure plate
Clutch disc
Release (throwout) bearing
Pilot bearing
Installation tool

1 Lightweight flywheel or equivalent (optional, from Suby Sports, Adam & Sons, iSR Performance)

3.5L Transmission oil (3.1 qts), a.k.a. 75W90 Gear Oil (optional)

2 Exhaust header gaskets (optional)

Shop rags, garage creeper, cardboard boxes to line the ground (optional)

Liquid Wrench (optional, strongly recommended)

Tools Required:

10mm, 12mm, 14mm, 17mm, 21mm socket (ratchet) wrenches

14mm deep socket wrench

18" or longer breaker bar

4" and 6" socket wrench extensions (optional)

10mm, 12mm, 14mm, 17mm open-ended wrenches

1 or more 2-ton floor jack(s)

4 2-ton jackstands

Small comealong or ratchet tie-down (optional)

Small flat-blade screwdriver (optional)

Let's Start

Disconnect the negative terminal from the battery. Wrap the cable in a rag to prevent any shorts. This is not aboslutely necessary, but is a good precautionary measure! Next, make sure you have all the parts necessary in the clutch kit. Then jack the car up and rest the car as high as possible on jackstands at all four corners using the recommended jack points. Spray rusted or siezed bolts with Liquid Wrench or WD-40.

Allow the car to sit until the exhaust pipes and headers are cool to the touch. The catalytic converter may still be warm, but that's OK. Remove the exhaust pipe and muffler. This is done by unbolting the two stainless steel bolts at the catalytic converter (cat-back) flange just behind the gear shifter, and unbolting the muffler hangers in front of the rear bumper. Disconnect the O2 sensor. The plug should be near the top on the right side of the transmission housing. Loosen the large hanger bolt just aft of the catalytic converter. Remove the six stainless steel nuts holding the exhaust headers to the bottom of the engine. Remove the large hanger bolt from the previous step, and take the exhaust header and gaskets out. Remove the aluminum exhaust heat shield. If you plan to change the transmission oil, drain the oil by removing the 21mm plug on the bottom of the transmission.

Remove the rear differential driveshaft cover. This will expose the propeller drive shaft flange bolts. Remove the four drive shaft bolts (yellow arrows point to where bolts were removed from). Note rear heat shield for exhaust piping (green arow). Remove the two bolts on the center driveshaft bearing (picture missing). Carefully lower the driveshaft and pull the entire prop shaft out of the transmission housing (picture missing). If you didn't drain the transmission oil, plug the transmission hole up with a plug or clean rag.

Use the floor jack or suitable support to hold up the transmission while you remove the 4 bolts at the rear cross member (rear cross member bracket shown by blue arrow) and the 2 bolts on the front cross member (front cross member shown by green arrow). Note the exhaust hanger bracket (yellow arrow). Remove the shifter linkage bolts; one bolt/nut set on the shifter pushrod, and one nut/plate set on the ball joint support (for lack of a better term). Edwin's finger is either pointing out the cardboard flap used to cushion the crossmember, or is showing off his finger strength.

Remove the air box from the intake manifold. There are quite a few hoses connected to the air box. Don't lose any of the clamps. Remove the air box support from the left side of the transmission housing. Remove the nuts from the two very long bolts at the bottom of the transmission housing. Remove the starter bolts and temporarily secure the starter away from the transmission housing. Remove all remaining transmission bolts with the exception of the top one (across from the starter). Disconnect the electrical plugs on the right side of the engine. Disconnect the gear sensor plug from the top of the transmission housing. Remove the bolt and nut from the transmission dogbone (pitching stopper). Double-check that the transmission jack is supporting the weight of the transmission, and then remove the remaining transmission bolt.

Slowly lower the transmission jack, and the top of the transmission housing should start to separate from the engine. You may need to pry them apart with a large flathead screwdriver to help in this. The engine will tilt as the transmission is lowered, and this is normal. Stop once a 4mm (1/4") gap is present between the transmission housing and engine. Next, use a suitable tool to slide the transmission housing away from the engine (we used a ratchet tie-down anchored to the rear control arms for this purpose). The transmission will be resting on the two very long lower bolts, so a little extra force may be required to pull the housing out over the threads. Slide the transmission housing out enough to provide room to get to the pressure plate bolts and release bearing with your hands. In the picture (left), you can see the stock pressure plate (red arrow), stock flywheel (blue arrow), dogbone (green arrow), and the hydraulic clutch cylinder (orange arrow).

Insert the Installation Tool into the clutch disc. Remove all the bolts from the pressure plate. Use a suitable tool to jam the pressure plate (or flywheel) and prevent movement while you remove the bolts. Remove the pressure plate, followed by the clutch disc. Use the handy installation tool to carry the clutch disc out. You will now see the flywheel (picture at right). Remove the eight flywheel bolts (green arrow) and flywheel from the engine crankshaft. You will have to find something to jam into the gear ring to prevent the flywheel from moving. Note the alignment pins (one shown by red arrow) If you are reusing the flywheel, a flywheel resurfacing is highly recommend (most auto shops should provide this service). If you are installing a lightweight flywheel, be sure to have the clutch surface finished beforehand (and the flywheel balanced - duh!).

Compare the two flywheels. The stock flywheel (left) weighs 25 lbs, while the Exedy lightweight flywheel (bottom) weighs 12 lbs. Note that the clutch faces for both flywheels are facing away from you. (Forgot to take pictures of the other size.) Install the new pilot bearing onto the flywheel. Use a suitable drift and hammer to gently tap the bearing into place until flush.

Compare the two clutch discs. The OEM Exedy stock clutch disc (left) is in excellent shape even after 25,000 miles. Both clutch discs are very similar in design and construction. Word is that the ACT clutch kit uses an Exedy disc as well, hence the similarity. No further prep is required for the clutch disc.

Finally, compare the two pressure plates. The only real difference is that the fingers on the ACT pressure plate (right) are thicker and wider than the stock pressure plate (left). No further prep is required for the pressure plate.

Install the alignment pins in the flywheel, if applicable (we actually forgot to install them, but fortunately the pressure plate seems to have been centered properly even without the alignment pins). Then install the flywheel onto the engine crankshaft. Torque flywheel bolts to 53 ft-lbs. Use the installation tool to hold the clutch disc onto the engine crankshaft, and install the new pressure plate. The installation tool holds the clutch disc until the pressure plate takes over. Torque pressure plate bolts to 12 ft-lbs. Remove the installation tool once the pressure plate is secured (see picture). Remove the old release bearing from the actuator fork on the transmission side (picture missing). There is a small steel retaining clip on each side that secures the release bearing. Install the new release bearing, and secure using the retaining clips.

Here's the hard part. Carefully pull the transmission housing back towards the engine, using the two long bottom bolts as a guide. Crank the engine a bit by hand and/or wiggle the transmission and engine if the pilot shaft doesn't seem to mate properly with the crankshaft at first. Once the transmission and engine are close, use the long top bolt to pull them together. Reinstall all the long transmission bolts, along with the starter and cable guide brackets. Note that the two longest bolts go into the top of the transmission housing (one through the starter flange). Reinstall the two nuts on the two long lower bolts. Torque transmission bolts and nuts to 37 ft-lbs, and starter bolt and nut to 30 ft-lbs. Reinstall the dogbone (pitching stopper) bolt and nut.

Reconnect the gear selector sensor plug. Reinstall the shifter linkages. Reinstall the bolts for the transmission crossmembers. Don't forget to install the corresponding cable guides and hangers. If the transmission oil was drained, fill the transmission with the required amount of gear oil. Verify gear shifter operation. Turn the crankshaft by hand, and check that the transmission rear output shaft turns as well. Reinstall the air box support. Reinstall the air box. Reinstall the driveshaft assembly. Resinstall the rear driveshaft cover. Reinstall the exhaust header. Don't forget about the exhaust header gaskets, and make sure to use the 14mm stainless steel nuts (the zinc plated nuts are for the bottom transmission bolts). Torque exhaust header bolts to 22 ft-lbs. Reconnect the O2 sensor, and secure the cable with the cable guide on the transmission housing. Reinstall the heat shield. Reinstall the exhaust pipe and muffler. Reconnect the negative battery terminal. Be prepared with the remote if you have an alarm. Start the engine and let it run for a few minutes. Then turn it off. Restart the engine and be prepared for a low engagement zone (close to the floor) when popping the clutch!

Standard disclaimer: This information is being provided as an educational and informational service for the Subaru community. I do not make any warranties, but I will be happy to help with questions about these modifications. Please proceed at your own risk!