My former tech, anime, and music blogging habits seem to have been overshadowed by car project updates. It is hard to write about other things when this is what I’m focusing on at the moment.
This time the work is on the gear and differential oils. The (2006) WRX has a front, rear, and center differential oil as well as gear oil. The front and center differentials and gears all share the same oil from the same location, 75w90. The rear differential is a limited slip differential which requires 90 PA oil for limited slip differentials.
What was in the car before? Hell if I know, but it was time for it to come out. The front fill point is located under the intercooler. A funnel with a hose attached makes it easiest to fill the front oil, so I picked one up to save the time needed to detach the intercooler and move it out of the way. The front drain point is in the center of the car on the front end and you can’t miss it. It requires a torx t-70 bit, which is unmistakable. Getting the plug out of the car was much easier said than done since its hard to get any kind of high torque when you’re laying on your back below the car. Let’s just say I was tired and relieved when I finally broke the plug off.
After the oil finished draining, I just dumped in the 3.7 liters of oil required for the front into the funnel and finished that job up. I didn’t snap any pictures of the rear since, at this point, I was covered in super glue (from an earlier project), Rust Bullet, and old gear oil. The rear differential is a bit of an odd change since both of the fill holes are horizontal, they’re not straight up or straight down. Both rear differential plugs require a 1/2″ ratchet drive to loosen and tighten them, how convenient. To make getting these plugs off extremely easy I used a jack below the wrench to break the plugs loose, quick and easy.
Once the oil was done draining filling the rear differential was a nightmare. I bought a hand pump from Autozone, but the damn thing didn’t work too well. I ended up cutting the tubing from the hand pump and taping it to the end of the hose on the funnel. I laid under the car with the end of the tube in the rear differential fill hole while my brother stood by the back of the car holding the funnel up. It was painstakingly slow to fill the rear and after our makeshift super funnel broke once, getting oil all over my blanket and me, we put it together once again and finished the fill. I put some threadlocker on the top plug, as I also did on the bottom, and tightened it back up.
On the rear differential, there is nothing to say. Is the Motul 90PA oil a huge improvement on what was in it? I guess I will know in 30k miles when I drain it to see how bad it looks, but at the moment everything in the rear is fine. So what about the front? The front is improved. The new oil is like night and day and shifts between first and second are smoother than ever. Second to third is smoother as well, but between third and fourth and fourth and fifth I don’t notice anything different.
Either way, the oil needed to be changed and it wasn’t the cleanest job on the planet. Good thing it only needs to be done once every 30,000 miles. I recommend going with Motul, you can and will tell a difference between it and other oils. There is a cocktail of oils I’ve seen floating around, but it seems like a little too much trouble for my taste.
