5spd Subaru WRX five speed manual tips and tricks

Subaru WRX five speed manual:

The viscous limited slip center differential is assembled with a thin circlip, which wraps around twice and holds all the internal spider gears and viscous coupler together. This clip isn’t like the old circlip, which is a 1 piece found in phase 1 5spd transmissions; ’91-’98. All of the ’99-09 5spd and through 2014 for WRX and Forester models uses this wrapping-around circlip.

5Spd: Center diff taken apart.
5Spd: WRX Center diff taken apart.

Over time the clip slips off and gets chewed by the transfer gears right behind the center differential. Sometimes you will find the clip in pieces, other times it gets shredded. The transfer gears themselves may also get damage along with the bearings in the transfer case. You won’t have to worry about this if you have the 6spd transmission; STI 6spd and 6spd on WRX/Legacy/Outback models.

5spd: A look inside at the spider gears
5Spd: A look inside at the spider gears of a WRX transmission
5Spd: Viscous coupling plates
5Spd: Viscous coupling plates

You have two options. A quick fix is to tack weld the clip to the rear cover. This will prevent the circlip from slipping off and keep it together. Your other option is finding a replacement differential either used or new to replace the broken one you have. From sources I’ve collected, the replacement center differential from the dealer will have the updated thick 1 piece c-clip.

Tack weld for what? Tack weld for dying center diffs!

5Spd: Center diff assembled. Don't mind the big washer. This center diff was gutted of its viscous plates and converted to an open diff for special purposes.
5Spd: WRX Center diff assembled. Don’t mind the big washer. This center diff was gutted of its viscous plates and converted to an open diff for special purposes.
5Spd: Tack welded clip
5Spd: WRX Tack welded clip