ICT Billet -6AN to 1/4 NPSM Transmission Adapter Pair, Aluminum, Fits TH350/TH400/4L60E

These ICT Billet adapter fittings convert -6AN male flare lines to 1/4" NPSM transmission case ports for a wide range of GM and Ford transmissions, sold as a pair with O-rings.

When building custom transmission fluid lines or replacing worn fittings, you need durable adapters that match factory case threads and seal reliably. ICT Billet's 551114 adapters are machined from aerospace-grade billet aluminum in Wichita, Kansas and designed to fit many popular transmissions including TH350, TH400, 4L60E, 700R4, 200‑4R, TR6060 and Ford AOD/4R-series, plus C5 manual cases. Each kit comes with two fittings and O-rings so you can install front and rear ports quickly.

Which transmissions and case holes will these adapters work with?

These fittings are made to be compatible with a wide selection of GM and Ford transmissions through model year 2007 and specific manual cases. They thread into factory 1/4" NPSM style ports so they match the common case design used on many vehicle platforms.

• Compatible transmissions: TH350, TH400, 4L60E, 700R4, 200‑4R, TR6060, AOD, 4R100, 4R70W, C5.
• Fits transmission case holes designed for 1/4" NPSM threads up to 2007 production.
• Designed for use with -6AN male flare hose ends and braided lines.
• Sold as a pair with O-rings for both front and rear ports.

How do these adapters help when building or repairing transmission lines?

These adapters let you connect standard -6AN braided or hard lines to factory transmission ports without welding or custom machining. They provide a reusable, serviceable connection and simplify routing by using widely available AN fittings and hose assemblies.

• Converts factory 1/4" NPSM port to -6AN male flare for standard AN hose assemblies.
• Allows easy replacement of damaged factory fittings or creation of aftermarket lines.
• O-ring seal reduces leak risk and permits repeated removal and reinstallation.
• Works with braided stainless lines, PTFE hoses, or hard AN lines.

What materials and construction details matter for durability and performance?

ICT Billet machines these adapters from US-produced aerospace-grade billet aluminum for strength, corrosion resistance and consistent thread tolerances. A quality finish and included O-rings ensure a reliable, leak-resistant installation even under repeated service.

• Aerospace-grade billet aluminum construction for durability and light weight.
• Precision-machined threads for accurate fit in factory case holes.
• Includes O-rings to ensure proper sealing without thread sealant or Teflon tape.
• Made in Wichita, Kansas — manufactured in the USA.

How do I install these fittings and what should I watch for?

Installation is straightforward: remove the factory plug or fitting, hand-start the adapter to avoid cross-threading, then tighten to a snug torque and install the O-ring for a proper seal. Confirm thread compatibility with your case and inspect the O-ring seating before final assembly.

• Remove factory port plug or fitting and clean thread area.
• Hand-start adapter into 1/4" NPSM port, then tighten with appropriate tool; avoid over-torquing.
• Ensure O-ring is properly seated and undamaged to prevent leaks.
• Attach -6AN hose end to the adapter and check for leaks during a test run.

Who this is for: These ICT Billet adapter fittings are ideal for mechanics, fabricators and vehicle owners building custom transmission cooler lines, replacing stripped or damaged case fittings, or converting factory ports to use standardized -6AN plumbing. Choose this pair if you need reliable, USA‑made billet aluminum adapters that fit a broad set of GM and Ford transmissions and come ready to install with O-rings.