The shift pistons in the valve body make contact with the forks and move them into position. If these pistons wear, the forks and sleeves will no longer shift properly and can be damaged. This is a common problem with the GR6. Prevention is to perform this TSB.
We have never encountered these problems again after performing this TSB so it has become standard procedure to install clips in every unit we touch.
APPLIED VEHICLE:2009 – 2011 GT-R (R35)
For 2009 - The MIL is on and DTC P0729 (6GR Incorrect Ratio) is stored,
For 2010 - The MIL is on and DTC P0729 (Sleeve A1 Function) is stored,
For 2011 - The MIL is on and DTC P2832 (Shift Fork A) is stored,
Here is a picture below of the wear. Note the circled area. It doesn't look like much, but that is enough to cause thousands of dollars in damage:
The clips will allow for better contact with the piston and prevent the wear or failure.
There are a series of magnets inside the piston which will become out of range of the sensor if the assembly wears too far. This will prevent the system from recognizing where the piston is moving and the unit will shift the fork too far as it doesn't know the forks location. This is what will break the fork along with the sleeve. Well worth performing while you have your pan out and this TSB can be completed while the trans is in the vehicle.