This DIY is part personal experience and a compilation of others post found on Tuners and ScoobyMods. If I can reference those posts I will, if not, it is not my intention to plagiarize.
-A few of the pics and specs I dug up from:
Manual Tranny Fluid change (auto front diff at bottom of page) - ScoobyMods
courtesy of Peaty.
My Wrex- an 04 WRX wagon. Significance? 04 and older, the Tranny drain plug is a 21mm bolt. Problem is, some 04 and all newer models use a torx bolt sized T-70. Before you start anything, crawl under your car and check it out. The standard bolt will look like the first attached picture. The Torx will look like the one near the bottom.
-A note before crawling under the car, the plug is supposed to be torqued to 32.5 ft/lbs but mine was significantly more. You may want to get yourself a cheater bar, a metal tube to add leverage, or you can buy a 3/8 ratchet with an extendable handle from the Great Satan (Walmart.) I managed to pop the seal on the plug with just a regular 3/8 ratchet but I am a big fella plus it cost me some rapped knuckles.
-A non-STi Tranny holds 3.7 quarts plus a little extra so pour the 3.7 then check the level with the dipstick and be sure you dont overfill.
-As for Transmission oil, I chose to go with a mix of 3 different oils called either the Grimmspeed cocktail or Uncle Scotties cocktail. They are the same mix just put together by 2 different folks. It is a mix of 1 quart Redline Lightweight Shockproof, 1 quart Pennzoil Syncromesh, and 1.7 quarts of Castrol Hypoy C 80w90.
-This can all be ordered from Grimmspeed along with the T-70 Torx bit. It cost me 67 dollars including 2nd day shipping to VA. The Torx bit can be a bitch to find, just an FYI.
-You will also need a funnel with about 2 feet of line. You can pick one up at your autoparts store or make one for some tubing and a funnel. You need this to pour your new oil.
Warm the car up with a quick drive but dont go to far because then the oil and manifold get hot making things a whole lot less pleasant to deal with.
1. Jack or ramp the car but make sure it is not on to great of an angle. Either chalk the wheels or make sure its not going anywhere as you may rock the car popping the seal on the plug.
2. Pull the transmission oil dip stick. This will allow the oil to drain out faster and take some more dregs with it.
3. BBBreaking the seal. I had to give it significant force to break the the seal so just beware. Once the seal is through you should be able to hand loosen from there. Make sure the copper ring seal is with the bolt as you do NOT want to go fishing in the oil pan for it.
4. The oil will drain quickly, faster than engine oil, so have your pan ready to receive it.
5. Clean and Inspect the plug magnet and copper ring seal. If the seal is bent or broken, you must replace it. If it is intact clean it well and reuse. The plug magnet will have some metallic slime and probably a few metal shaving attached. If there is alot of metal, you really need to reevaluate how you shift!
6. Replace the plug and seal. Use a torque wrench if you have one and if not, tighten just enough. Do not over torque the bolt, the copper seal can crush and then the plug will leak.
7. This is the fun part. Borrow another pair of hands to hold the funnel and line. If you dont have someone to help just take your time, act slowly, and hold securely. Put your Redline and Pennzoil in first. Add one quart of Castrol. I measured off the .3 quarts not to be used from the last by using an old kitchen measuring cup. 1.2 cups is .3 quarts. Put the measured off portion into the empty Castrol bottle as you will probably need some of it later on.
8. Pour slow! Take your time and let the line drain after each pour. It is very easy to either remove the line from the inlet or miss it entirely. Going slow allows u to make sure the oil is going where it needs to. See picture for placement.
9. Clean dipstick and check oil level, add more if needed.
10. Take your car out for a warm up and then check for any leaks when u get back! CHeck the oil level after a few days of driving to make sure u dont need to add.
11. A BIG FYI, if you get oil on your engine or manifold cover clean it off well with soapy water. If you let it stay, the fumes will invade your car for a LONG time. Tranny oil is some potent stuff.
There ya go. I hope this helps guys. You are welcome to message me if you would like some more info. Check out the pictures and captions for what the process looks like.