On higher gear your car transmission pops out while driving.
Car Problem Diagnosis
Manual transmission is a complex part, when this kind of problem occurs the possible cause is the problem on shift linkage or something called the input shaft. If this part is faulty it can cause the transmission to pops out of higher gear. The shift linkage and the degree of the input shaft movement have a lot to do with the transmission staying in gear. When these two parts is worn or out of adjustments or when the input shaft has an excessive play, it causes the transmission pops out of higher gear.
The transmission troubleshooting we provide is just a possibility, we can only confirm the problem once the actual part is opened up and inspect. Other possibilities can cause this problem and can only be determined by a mechanic.
All About Auto Advice
There are no other options but to bring the car to a reputable auto repair shop specializes in transmission repair, and ask the mechanic to check the actual part. Probably, the mechanic will just adjust the shift linkage to fix the problem. However, if the problem still occurs, then the mechanic will have to tear down the transmission to inspect and determine the cause of the problem. When this is the case then you will be facing a costly repair. Just hope that the transmission is still under warranty so that the repair is covered.