Can a Car Run While Adding Transmission Fluid?

The answer to this question is a resounding no. Adding transmission fluid to a running car can be extremely dangerous and should never be attempted.

Why is it dangerous to add transmission fluid to a running car?

There are several reasons why adding transmission fluid to a running car is dangerous:

The transmission fluid can overheat. When the transmission is running, the fluid is constantly being circulated and heated. Adding more fluid to the system can cause the fluid to overheat, which can damage the transmission.
The transmission fluid can foam. When the transmission fluid is agitated, it can foam. This can cause the fluid to lose its lubricating properties, which can damage the transmission.
The transmission fluid can leak. When the transmission is running, the fluid is under pressure. Adding more fluid to the system can cause the fluid to leak out of the transmission. This can lead to a loss of fluid, which can damage the transmission.

What should you do if you need to add transmission fluid?

If you need to add transmission fluid to your car, you should always do so with the car turned off. Follow these steps to add transmission fluid safely:

Park your car on a level surface. This will help to ensure that the fluid level is accurate.
Turn off the engine. This will prevent the transmission fluid from overheating or foaming.
Locate the transmission dipstick. The dipstick is usually located near the front of the engine.
Pull out the dipstick and wipe it clean with a rag.
Reinsert the dipstick into the transmission and pull it out again. The fluid level should be between the two marks on the dipstick.
Add transmission fluid to the transmission as needed. Use a funnel to add the fluid slowly. Avoid overfilling the transmission.
Reinsert the dipstick and check the fluid level again. The fluid level should now be between the two marks on the dipstick.
Start the engine and let it run for a few minutes. This will help to circulate the new transmission fluid.
Check the transmission fluid level again. The fluid level should still be between the two marks on the dipstick.

Conclusion

Adding transmission fluid to a running car is extremely dangerous and should never be attempted. If you need to add transmission fluid, always do so with the car turned off. Follow the steps above to add transmission fluid safely.