The car will go into safe mode while driving and the display will say gear box fault. What do i need to do?

Is the check engine light displayed? If it is, that's where you start, by retrieving the fault code(s). If not, then you could have a security system fault, fuel system breakdown, etc. All codes, regardless of the systems affected, will cause the vehicle computer to immediately default to a failsafe mode, till the problem has been fixed, and this drastically affects driveability, causing no-start issues, idle problems, etc.

BMW has been using electronically controlled automatic transmissions in most models since the late 80s. These transmission systems employ a transmission control unit which controls electrical solenoids to manipulate the various control and shift valves and functions in the transmission valve body. When the transmission control unit detects a problem that it thinks could be damaging to the transmission or engine, it goes into a fail-safe or limp mode. In this mode, the transmission will function in reverse normally, but in forward it will operate in only one gear (whether you have the shifter in D, or any of the lower gears). This will typically be 3rd or 4th gear, depending on the model. It will start in this gear and stay in this gear with no shifting. You would experience this as sluggish acceleration and higher than normal engine speed at about 40 mph and above.

If you must drive the vehicle when the transmission is in the fail safe mode, accelerate gently and keep the road speed lower than full highway speed.

Earlier models do not employ fault codes and must be diagnosed manually. Late models do employ fault codes and a diagnostic/scan machine can be used to check and read the faults to assist in diagnostics. Note that this is not your common OBDII engine management fault code tool. This is what A BMW dealer or a properly equipped independent shop would have for full vehicle system diagnostics and coding operations.

the message "fail safe mode" is telling you that there is a fault in either the engine or gear box. In your case the problem is in the transmission. Run the fault codes and check for a torque converter servo/solenoid failure or a TCM problem. Check that there is oil in the transmission.

According to your words, I strongly believe you do have a problem with your transmission.to what you have up to now on driving and locked to a gear means there is a fault and the gear box gets into a Safe Mode to allow you go to a garage for inspection and repair. On by switching off and on driving is not the correct procedure because having that means you do clear the fault code (s) and run for awhile and back to the beginning. My skills advise just visit a qualified garage to use a Scanner in order to get the faults and repair.

you can drive it still. but limited. or maybe your engine oil need to be change

The vehicle would seem to lose power as the transmission has gone into 'safe mode' and the transmission control module has detected a fault in the transmission hence the flashing gear display. you need to get someone in a dealer or someone that has the technology to plug into the car and find out what the problem in the trans is. hope this helps.

NEEDS TRANSMISSION FRONT DRUM BROKEN

whats the fault code in the tcm? you should only need to clear the codes

fail safe mode should give you third and reverse

fault in the TCU or a soleniod failure

You have a bad gearbox position sensor located on the transmission. When the transmission computer sees the fault in that sensor it goes into a protective mode in your car starts out in second gear that's why it is sluggish. This is a very common failure on that car. The heater issue is not related.