Question: how do you know when your vehicle needs transmission fluid?
Answer: Trouble Shifting Gears. One of the common symptoms of car problems is the abrupt hard shifting of gears. ... 
Transmission Slipping. Another common issue is transmission slipping. ... 
Unusual Noise. In general, the transmission of the vehicle should be noiseless. ... 
Transmission Overheating. ... 
Transmission Fluid Leaks.