Your Subaru Impreza’s torque converter is responsible for converting the energy generated by the engine at the flywheel and transferring it to the transmission, creating a bridge between the engine and the transmission.
In the Subaru Impreza, a bad torque converter is often caused by bad transmission fluid, worn clutches, bad seals, or loose bolts. Symptoms of a bad torque converter include a vibration, too much RPM on the highway, and slipping.
Bad Torque Converter Symptoms: Subaru Impreza
Here are some of the most common bad torque converter symptoms that could happen to your Impreza.
1. Slipping Transmission (Low Speed)
The torque converter “stall speed” is the speed that the engine needs to be turning before the torque converter will begin engaging the transmission. When a torque converter is malfunctioning it can cause this stall speed to change and feel like the transmission is slipping. If you suspect this is happening with your car, has your fuel mileage changed? This is often a sign that the transmission isn’t operating efficiently.
More Info: Impreza Transmission Slipping Diagnosis
2. Slipping (Higher Speed)
Nearly all modern automatic transmissions have a locking torque converter. A locking converter has clutches in it that lets the transmission make a physical connection with the engine. This eliminates operating inefficiency when it is at high speed (usually after about 45 miles an hour). This increases the fuel mileage achieved and brings an automatic transmissions efficiency more in line with a standard transmission.
3. Bad Fuel Economy
If the torque converter has gone bad, then it’s no longer transferring power to your Impreza’s rear wheels in an efficient manner. This keeps your Impreza’s engine from turning at the right RPM for any given speed, which can really hurt fuel economy. When this happens, your torque converter has a higher effective stall speed.
4. Shuddering
Torque converters use a lock up clutch to create a true 1:1 connection between the engine and the wheels. It won’t do this at lower speeds so your Impreza can take advantage of the torque multiplication that a torque converter provides.
If the torque converter fails to unlock at lower speeds, it shudders. This shudder feels like a manual transmission when you need to downshift.
5. Sounds
A bad torque converter will often make strange sounds. The best way to describe the sound would be a whir sound if you have bad bearings in it and a clunking sound if it’s a bad turbine fin.
6. Bad Transmission Fluid
Like your automatic transmission, the torque converter is full of transmission fluid. This fluid helps cool the converter and transfers energy. If your Impreza has bad transmission fluid, it can cause the torque converter to go bad.
Taking a look at the transmission fluid should be the first thing that you do. It can tell you a lot about the health of your transmission in general.
Causes of Torque Converter Problems: Subaru Impreza
There are many different things that can cause your Impreza to have torque converter problems. Here are the most common ones.
1. Low or Dirty Transmission Fluid
Transmission fluid is the lifeblood of the transmission and the torque converter bolted to it. If there isn’t enough it can’t do its job. This will in turn cause the transmission to overheat.
This is one of the most common causes of torque converter problems. If the transmission fluid is dirty and old it won’t be able to do its job as a hydraulic fluid as well. This can lead to a feeling of extra slipping and chattering at speed.
Make sure you take a look at the fluid before you do anything with your transmission. If you don’t know or can’t remember the last time it was changed or serviced this would be the place to start. Here’s a transmission fluid color chart.
2. Worn Clutches
The clutch that locks the transmission to the engine at highway speed can wear out just like a normal manual transmission clutch.
3. Bad Seals
This is one of the most common issues that causes a torque converter to go bad. It’s usually pretty detectable, as there will be a pool of fluid underneath your Impreza.
4. Loose Torque Converter Bolts
This will create the same symptoms as the bad seals in that the converter is going to puke a bunch of ATF all over your garage floor, but you should also be feeling quite the vibration at speed.
If you suspect this could be what is going on with your transmission, just know that if those bolts come all the way out the least that is going to happen is that it disengages from the input shaft. Most likely it’s going to really do some real damage to the crank and input shaft.
Faulty Torque Converter Diagnosis
Before trying to diagnose whether your Impreza has a bad torque converter, you’ll want to drive to let the transmission warm up to its normal operating temperature. It takes a bit longer for the transmission to warm up than the engine.
Give it a few extra minutes after the engine warms up all the way. This will ensure that the transmission is shifting as it would nearly all the time that it normally operates.
Pay attention to what’s going on with both your Impreza’s engine and transmission. Pay particular attention to any shuddering and vibration as you accelerate. Shuddering and vibration are in no way a guarantee that something is wrong with the torque converter, but they are a strong indicator there could be something wrong.
Conclusion: Impreza Torque Converter Problems
It’s hard to get to your torque converter, which means that you have to rely on observation to determine if the torque converter is going bad. This makes diagnosing torque converter problems challenging. Good luck with your Impreza!