I just cracked open a 2009 TSX 6-speed transmission to install a Quaife LSD for a friend of mine only to find the OE differential and ring gear is of the 14-bolt variety... YIKES !!! Since both the 8th gen Civic Si and the TSX 6-speed have the same 4.764 final drive, I am considering the idea of installing the Civic Si countershaft and ring gear since that ring gear is a more conventional 10-bolt style. The countershaft factory part numbers differ... so I hate to convince him to spend the money on them if they won't work. Has anyone done this... and if my solution is not the appropriate one, what did you do differently ???

Aquafina... your thoughts ???

 

The P/N could be different for any number of reasons. I would change out to an MFactory FD if money is going to be spent. It will cost more but is the best bang for the buck you can get. Otherwise just swap in a good used matching FD.

 

Didn't have a used FD ring and countershaft laying around, so I ordered one of each. Once they arrive, I will update this thread as to what ultimately worked.

 

UPDATE !!! The 8th Gen Si ring gear and countershaft (Honda part # 23227-PZF-315 ) worked like a charm. I got new differential bolts as well. Also, the sixth gear on the mainshaft is much like the 8th Gen Si if you would like to change it out for a taller gear. It is a single synchro set-up instead of the earlier TSX style dual synchro type. I used the 23590-RAS-A00 gear on the mainshaft and the 23491-RAS-000 on the countershaft.