Converting a Subaru automatic transmission such as the 4EAT or 5EAT to a two-wheel drive (2WD) layout is one of the most popular steps in Volkswagen-running Subaru drivetrain builds. It allows you to shed AWD weight, simplify drivetrains, and tailor performance for mid-engine or rear-engine setups.
However, these conversions are intricate, and even small oversights can cause catastrophic failures or expensive rebuilds. As a Volkswagen-running Subaru drivetrain auto parts manufacturer, we’ve seen what goes wrong most often. Below are the five biggest mistakes to avoid so your 2WD automatic build runs reliably for years.
1. Choosing The Wrong Kit For Your Rotation Needs
What Goes Wrong
Many builders don’t confirm the rotation direction their build requires. Subaru automatics were designed for AWD setups, so when they are converted to 2WD, rotation must match your axle layout.
Why It Matters
- Using the wrong rotation direction causes the wheels to spin backward in mid-engine layouts.
- Incorrect rotation can damage differentials or create unusable gearing ratios.
- Fixing this error later requires a complete teardown.
How To Avoid It
- Understand your build’s layout (front-engine vs. mid-engine).
- The 5EAT 2WD and standard 4EAT 2WD conversion kits maintain original Subaru rotation.
- If your mid-engine setup requires the opposite rotation, use the 4EAT 2WD Reversed Rotation Kit specifically made for that purpose.
Pro tip: Decide on your layout first, then select the right conversion kit. This eliminates trial and error and prevents costly mismatches.
2. Leaving The Rear Output Unsupported Or Unsealed
What Goes Wrong
Some builders simply remove the AWD center differential parts and leave the rear output shaft area open, unsupported, or poorly blocked off.
Why It Matters
- Open housings allow dirt, dust, and moisture to enter the case.
- Unsupported shafts or bearings can float and wear out prematurely.
- Leaks from unsealed housings cause fluid loss, overheating, and failure.
How To Avoid It
- Use a conversion kit that properly eliminates the AWD output section.
- Confirm that the rear section is sealed and the bearings are supported after assembly.
- Only use quality gaskets and sealants recommended for ATF-exposed surfaces.
Important Distinction:
If you are converting a manual 5-speed to 2WD, use a Subaru transmission cap for the extension housing to seal the back of the nose cone. This part is not for automatics but is essential in manual conversions.
3. Skipping Oil Pressure Checks On The Engine Side
What Goes Wrong
Builders often focus entirely on the transmission but ignore the engine’s oil pressure system during conversion. This is risky, especially with Subaru EJ253 engines, which are commonly paired to automatic transmissions in conversions.
Why It Matters
- EJ253 engines are known to develop cracks at the oil pressure sensor port on the cylinder head.
- This causes inaccurate pressure readings or oil leaks that can harm the engine.
- Bad oil pressure data can confuse your ECU, affect shifting logic, and ruin an otherwise sound build.
How To Avoid It
- Before final installation, confirm actual oil pressure on the engine.
- Repair any oil sender port damage using a dedicated Oil Pressure Sensor/Sender Repair Kit for Subaru EJ253 engines.
- Only proceed with transmission installation once correct oil pressure is confirmed.
Pro tip: Fixing this early prevents having to pull the entire drivetrain back out just to patch a leak or sensor error.
4. Overloading Stock Internal Parts Without Reinforcement
What Goes Wrong
Many people assume the stock 4EAT or 5EAT internals will survive new loads, aggressive driving, or performance upgrades. That’s rarely true.
Why It Matters
- Transmission internals are tuned for factory torque and load.
- Mid-engine swaps often create new stress angles and higher shock loads.
- Stock gearsets, bearings, and torque converters may overheat or fail.
How To Avoid It
- Inspect and refresh wear items like clutches, seals, and bearings before conversion.
- Consider upgrading gearsets or torque converters if adding power.
- Make sure mounts, brackets, and cooling systems can handle the load.
Pro tip: Our conversion kits are designed for heavy-duty use in performance and off-road builds, with carefully matched internals to withstand higher torque.
5. Neglecting Fluid Specs, Cooling, And Maintenance
What Goes Wrong
Fluid management is often an afterthought. Using the wrong ATF, skipping filter replacements, or ignoring heat control can quickly destroy a converted automatic.
Why It Matters
- Automatic transmissions rely on clean, correct-spec ATF for pressure and lubrication.
- Heat kills seals, solenoids, and clutch packs faster than anything else.
- Relocated or custom setups can restrict cooling airflow, accelerating wear.
- Some builders also add custom oil pans without realizing how oil slosh affects pickup.
How To Avoid It
- Always use Subaru-spec ATF and change it regularly.
- Install or upgrade external transmission coolers if airflow is reduced.
- Keep filters clean and watch for debris on the magnets.
- If using a pan without baffles, avoid prolonged high-g corners until you verify stable pressure.
Pro tip: Combining proper cooling with clean ATF is the easiest way to double the lifespan of a converted automatic transmission.
About Us
Specialised Parts is a Volkswagen-running Subaru drivetrain auto parts manufacturer and supplier. We produce precision-engineered components such as Subaru automatic transmission 4EAT and 5EAT 2WD conversion kits, 4EAT reversed rotation kits, EJ253 oil pressure sensor/sender repair kits, reversed ring & pinion gearsets, and short shifter assemblies.
Our products are manufactured for Subaru parts but are compatible with many vehicles that use Subaru components, especially VW builds. Compatibility varies by model, and our team is here to help you select the correct parts.
Contact us today to get the right components for your Subaru-to-VW drivetrain conversion and build your 2WD setup for reliability and long-term performance.
