A couple weekend project updates. I've already posted this picture before, but it pertains to the update, so I'll post it again. After I had finished pulling the powertrain out of both cars, I had two different R180 rear differentials. The one on the left is from the 04 sti and has 3.90 gears, and the one on the right is from the 2012 and has 3.54 gears. I wanted to retain the original 3.54 gears in my car, but the transmission I will be using has a 3.90 front gear set. From what they tell me, mixing front and rear gear ratios is bad. So, I found a donor transmission that had 3.54 front gears that would work in my transmission, which I received this week. To remove the front gear set, the first thing I did was split the front differential case from the rest of the transmission. To remove the differential from the case, I just unscrewed the bearing retainers on both sides, where the front axles go, and the differential was free to pull out. To remove the pinion gear, I took off the rear section of transmission and removed the large nut on the pinion shaft, and the 4 bolts holding it in front. After I did this, I was able to tap it out pretty easily with a mallet. Since I was going to have the ring and pinion gears cryo treated before they went into my transmission, I decided to remove the gears in the rear differential too, and have them all done at the same time. First I removed the large nut on the pinion shaft and used a puller to remove the yoke. After that, I took off the rear cover and the bearing retainers on the sides, pulled the differential out, and tapped out the pinion shaft. Front and rear 3.54 ring and pinion sets.