About this item
EVIL ENERGY 6AN Male Flare to 1/4" NPSM Transmission Cooler Line Fitting Adapters — CNC-machined from 6061-T6 aluminum with anodized finish. Designed to convert pre-2007 transmission cooler ports to 6AN flare connections for braided hose and AN plumbing upgrades. Includes 2 fittings.
Key Features
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Precision Conversion: 6AN Male Flare (9/16-18 UNF) to 1/4-18 NPSM Male — the most common size for TH350, TH400, 4L60E, and 700R4 transmission cooler line ports (pre-2007). Enables seamless AN braided hose plumbing.
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6061-T6 Aircraft Aluminum: Machined from solid billet, not cast or stamped. Silver anodized finish resists oil, rust, and corrosion for long-term under-chassis durability.
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37° Flare Seal: AN male side achieves a reliable, leak-free seal at the 37-degree flare cone angle — the industry standard for high-pressure fluid systems.
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Hex-Shaped Body: CNC-machined hex design allows easy tightening with a standard wrench. No special tools required for installation.
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Multi-Fluid Compatible: Safe for transmission fluid, engine oil, fuel, water, and other automotive fluids. Not limited to transmission cooling applications.
Fitment Guide — Read Before Ordering
| Transmission |
Port Thread |
Year Range |
Compatible |
| TH350 |
1/4-18 NPSM |
1969–1986 |
✅ |
| TH400 |
1/4-18 NPSM |
1964–1990 |
✅ |
| 4L60E / 700R4 |
1/4-18 NPSM |
1982–2006 |
✅ |
| 4L80E |
1/4-18 NPSM (different port design) |
1991–2006 |
❌ |
⚠️ Always verify your transmission's port thread size before ordering. Measure with a thread pitch gauge if unsure. This fitting is NOT compatible with inverted flare (IF) ports — it seals via a 37° cone, not an inverted flare seat.
Package Contents
- 6AN Male Flare to 1/4" NPSM adapter fitting × 2
- NBR Sealing O-Rings × 2
37° AN Flare Seal Design for Leak-Resistant Connections
The 6AN male flare side uses a standard 37° AN flare sealing surface to create a reliable metal-to-metal connection with compatible AN hose ends. The opposite 1/4-18 NPSM male thread is designed for compatible transmission cooler ports, providing a direct conversion from factory cooler fittings to AN plumbing systems.
Designed for Automotive Fluid System Applications
Designed primarily for transmission cooler line applications, this adapter provides a secure connection solution for compatible automotive fluid systems. The corrosion-resistant aluminum construction is suitable for applications involving transmission fluid, oil, and other automotive fluids when the fitting specifications match the system requirements.
How Should the Transmission Cooler Adapter Be Installed?
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Verify the port first: Confirm that the transmission cooler port uses a compatible 1/4-18 NPSM thread and accepts the adapter's O-ring sealing style.
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Inspect the O-ring: Make sure the O-ring is correctly seated and free from cuts, flattening, dirt, or twisting before installation.
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Start the fitting by hand: Thread the adapter into the port by hand to reduce the risk of cross-threading the transmission case.
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Tighten from the hex body: Use the machined hex section and follow the transmission or product-specific torque requirement. Do not apply an unverified universal torque value.
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Connect a matching hose end: Attach a 6AN female 37° flare hose end. Do not apply thread tape to the AN flare sealing surface.
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Inspect after operation: Restore the correct transmission fluid level, run the system, and inspect both cooler ports and hose connections for seepage.
Route cooler hoses away from exhaust components, sharp edges, and moving parts. For a complete system, compare compatible transmission oil cooler kits before selecting the remaining hose and cooler-side fittings.
Why Choose EVIL ENERGY Transmission Fittings?
EVIL ENERGY is a direct manufacturer of performance fluid system components — no middlemen, no markup chains. Our transmission cooler fittings are CNC-machined from 6061-T6 billet aluminum in our own facility, anodized in-house for consistent color and corrosion protection. Every fitting thread is cut to SAE specification for a drip-free seal at the 37° flare cone. Backed by US-based FBA inventory with fast Prime shipping and a dedicated support team. Whether you're converting a street car to AN braided lines or building a full race transmission cooler setup, EVIL ENERGY delivers pro-grade reliability at direct-factory pricing.
