The GT1R R35 Transmission Overflow Kit is designed to allow you to be able to over fill the transmission with fluid to ensure no air is sucked up by the transmission oil pump under high G's.  Without doing so, the pump will suck up air and cause transmission pressure to drop enough to lose clutch pressure and/or not shift.  If you over fill without a catch can the trans will spill oil on to the track at high G's.  We recommend 3.5 quarts over full and the Dodson Anti Surge plate in combination with our overflow kit.  The overflow can is to be installed in the drivers side (LHD car) rear wheel well.  The installation is very straight forward as seen in the below pictures. 

Step 1 - Remove this plastic clip

Step 2 - Drill that hole out to 1/2".  When enlarging an existing hole, a unibit works very well and a standard unibit goes up to half inch.

Step 3 - Insert one of the supplied well nuts into the new hole.

Step 4 - Temporarily mount the can to the first insert using the top mounting hole in the bracket.  Align the can so it's straight and mark the 2nd hole location.

Step 5 - Drill the marked location for another 1/2" hole.

Step 6 - Insert the second well nut in this hole.

Step 7 - Bolt the can in place using the supplied 1/4" bolts and washers.  The well nuts are rubber and will compress as the bolts are tightened, sandwiching the sheet metal.  You will feel a change in resistance when they get fully compressed.  They don't need to be too tight, snug it up a little after you feel the change from the insert not compressing anymore.

Step 8 - Install the hose on the bottom of the overflow and the breather vent on the transmission.  If the trans is out of the car, put the hose on the trans first with the hose clamp and attach to the can once the trans is in place.  If the trans is in the car, you can work the hose on to the barb without dropping the transmission, but you will not be able to put the hose clamp on that end.  This is fine though because it's a good fit and there's no pressure there.