Automatic transmission fluid (ATF) has two main purposes:
First, it is the lifeblood that enables a transmission to transfer power from the engine to the pavement. The torque converter uses ATF to form a hydraulic circuit in order to transfer rotational force from the engine to the transmission.
Its second purpose is to cool the transmission by absorbing the heat created by all its moving parts and expelling the heat through the radiator.
If a leak develops or a faulty component causes the transmission to lose fluid and you continue drive with a low fluid level, you may experience one or more of the following symptoms:
In This Guide
- Transmission Slipping
- Delayed Gear Engagement
- Hard or Erratic Shifts
- Car Won’t Shift
- Overheated Transmission
- Transmission Failure
- Checking your Transmission Fluid
You’ll know that your transmission is slipping when it makes a gear change, but then seems to falls back out of that gear. Other symptoms include abrupt up/down shifts, unusually high RPMs before a shift, erratic shifting, and a groaning or grinding noise coming from the transmission.
These problems may indicate that your vehicle is low on fluid, (which can cause it to overheat) and the friction material on the clutches and transmission bands are no longer able to securely engage a gear. This is a bad sign because it’s very likely that excessive wear/damage has already occurred.
2) Delayed Gear Engagement
Being low on fluid can cause a noticeably longer delay when you select Drive or Reverse, because there isn’t enough fluid pressure to immediately actuate the gear change. It may take 2-3 seconds before the selected gear actually engages, leaving you with plenty of time to ponder the fact that you haven’t checked your transmission fluid lately.
3) Hard or Erratic Shifts
Another sign is when your vehicle starts shifting erratically (shifts come later or sooner than normal), or it sort of bangs/slams into gear. An automatic transmission relies on hydraulic pressure to change gears, and a lack of ATF can have a negative impact on both shift timing and smoothness.
4) Car Won’t Shift
If there’s absolutely no ATF left in a transmission, it simply won’t work. No Drive, no reverse, nothing. Refilling the transmission with the correct type of ATF may bring it back to life in some cases, but you’ll still need to figure out how it got that low in the first place.
Since ATF is responsible for cooling the transmission, not having enough of it can cause it to overheat – very quickly.
Signs of an overheated transmission include delayed or erratic shifts, slipping between gears, loss of power, smoke and/or a burning smell. If this happens, pull over immediately and let the transmission cool down. Temperatures in excess of 240 degrees can cause serious internal damage, so you really don’t want to keep driving.
Transmission Heat Damage
- 220 degrees – varnish starts to form on metal parts
- 240 degrees – seals begin to harden
- 260 degrees – clutches & transmission bands slip
- 295 degrees – call a tow truck
6) Transmission Failure / Replacement Needed
If any of the above symptoms persist after you’ve topped off the ATF, then it’s very likely that your transmission will need to be rebuilt or replaced. In this case, here are 8 options to choose from.
Checking your Transmission Fluid
The problems listed above can lead to some very costly repairs if they are not taken care of.
To avoid this, start checking your fluid on a regular basis. If you put a lot of miles on your vehicle or tow heavy loads, then you should check your ATF at least every 2 weeks. Otherwise, most drivers can check it once a month (unless there’s a leak).
• Always leave the motor running when checking the fluid
• Consult your owner’s manual to determine the correct type of fluid for your vehicle and the proper way to add ATF
What to Read Next
- Transmission Fluid Leak Repair Cost
- How to Check Transmission Fluid
- Overheated Transmission: How to Avoid
- Common Transmission Problems
Over to You
We’re interested to know – which of these symptoms are you experiencing?