So, with the 2011 STI tranny it has a 1.1:1 center diff, which requires a 3.54 FD rear diff. I decided to go with the simple option and stick with the r160 in the rear, instead of the r180. The 02-05 WRX r160 is a 3.54 FD, so that is what I got. I also picked up a used 08+ AT driveshaft, 08+ STI shift linkage, ACT clutch setup, and some other small things. Here's a complete list of what I used:
Used 2011 6MT transmission
- 3rd Gear Synchros
- 4th-6th Carbon Synchros
- 3rd/4th Sleeve & Hub
- 3rd/4th Shift Fork
- 5th Drive Gear 6MT Long Ratio
- 6th Drive Gear 6MT Long Ratio
- 5th/6th Driven Gear Cluster 6MT Long Ratio
- Woodruff Key, Adapter (Wide shaft keyway groove)
ACT XT 6 Puck Clutch
- ACT XT Pressure Plate
- ACT 6 Puck Solid Disk
- ACT TOB and Pilot Bearing
- Resurfaced OEM Flywheel
- STI Clutch Fork
- STI Clutch Slave Cylinder
- Braided SS Clutch Line
08+ STI Shift Linkage
- STI Shift Linkage Bushings
- STI Front Shifter Bushings
- STI Rear Shifter Stay Bushing
- STI Shifter Lever
- STI 6MT Pivot Bushings
- Transmission Crossmember Bushings
- 08+ Impreza AT Driveshaft
- R160 3.54 Final Drive Rear Diff
- Heavyweight Shift Knob
- STI Starter
I decided to do the TIC/Kartboy shifter and bushing combo because it would be easy to do while it was all out of the car. The 6 speed lever is a bit more work to get installed than the 5 speed, but overall it wasn't too bad. Having it outside of the car wasn't really all that much easier, except for a few parts (front linkage bushings).
For the clutch I chose the ACT XT with 6 puck unsprung disk. I previously had the ACT HD and 4 puck sprung disk in my 5 speed. It chattered quite a bit, but I needed it to hold the torque. On the 6 speed I considered a twin disk, but the cost and frequency of rebuilds turned me off from it. The ACT is simple and can hold the power. The cost of a new disk is quite low. I chose the unsprung disk for lower mass on the tranny side (a little bit easier on the synchros).
The install went pretty smoothly. I've pulled and installed the 5 speed. clutch, driveshaft, rear diff, etc before, so most of it wasn't new. Just different parts. Pulling this shifter linkages completely out was new, but that was straight forward. The clutch setup (pull vs. push) is also a bit different. Also the 6 speed is much larger and heavier than the 5 speed, but with a tranny jack it wasn't too difficult to get it all into place.
FYI - All the connectors are plug and play. No issues there. The stock shift boot and boot insulation can easily be modified to work with the 6 speed. All I used was a scissor and some careful placement/folding and it looks like a perfect fit (see photos below).
Overall I am very, very happy with it. This shifts are so precise. I don't know how much of this is due to the full bushing and shifter kit, and how much is the tranny, but I do know that the 5 speed never felt this good, even with shifter and front and rear bushings.
The clutch pedal is noticeably heavier than it was with my other setup, but not too bad for daily use. I have the clutch delay valve removed (as I did with the 5 speed), and I find that this setup actually chatters less than my old one. The unsprung puck style disk grabs extremely quickly, but as long as you keep the revs very low and let out the clutch fast/smooth it is pretty easy to deal with.
The gear spacing is great! 1-5 are all just a bit shorter than they were with the 5 speed, so acceleration seems a bit quicker. 6th is longer than 5th was, so it's nice for cruising. So far I think this is a great set of gear ratios for daily driving and higher powered track cars.
Right now I'm still running the center diff open, but I will installing the DCCD Pro soon, and I can update at that time.