The trans failsafe mode means that the computer has gone into a safe mode because it is having a problem figuring out what to do, when to shift, etc. That can be a low voltage from the battery, any one of a number of sensors, an engine issue, or a transmission issue. Recommend you get the codes read by someone who can diagnose it properly. It may or may not be anything to do with the gearbox, and your gear box shop may not have the capability of troubleshooting the root cause.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue