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Small black plastic antenna adapter with coaxial connectors at each end, approximately fifteen inches long

METRA

METRA 40-GM18 antenna adapter car electronics accessory

SKU CH-RXZ5-E9BW4

Adapts a factory GM antenna cable to an aftermarket radio, measuring 15.00" long and weighing 0.07 lbs

  • Product typeInstallation Tools
  • Key featuresUsed To Adapt Factory Antenna Cable Connection To That Of An
  • Overall height0.5 in (1.27 cm)
  • Overall width2 in (5.08 cm)
  • Overall length15 in (38.1 cm)
  • Product weight0.07 lb (0.03 kg)
  • Adapts factory GM antenna cable to aftermarket radio
  • Compact 0.50 in height fits tight dash spaces
  • 00 in width allows easy routing behind panel
  • 00 in length reaches most head-unit locations
  • Lightweight 0.07 lbs adds negligible load to harness

Antenna Adapter for GM Vehicles

The METRA 40-GM18 is a new car electronics accessory that converts a factory General Motors antenna cable for use with an aftermarket radio. It functions as an installation tool to bridge the connection between the vehicle's original wiring and the new head unit. The adapter measures 15.00 inches in length, 2.00 inches in width and 0.50 inches in height.

Suits Radio Replacements in GM Cars

This adapter suits installers replacing a factory stereo in a compatible General Motors vehicle where the antenna plug differs from the aftermarket standard. It is not for buyers who need to connect an aftermarket antenna to a factory radio or those working on vehicles outside the GM antenna interface. The lightweight design at 0.07 lbs adds minimal bulk behind the dashboard.

Maintains Signal Integrity During Extended Use

Under sustained operation the passive connector maintains a stable RF path between the vehicle antenna mast and the receiver tuner. No active electronics are present to generate heat or degrade over long driving periods. The fixed cable length of 15.00 inches routes cleanly within the dash cavity without tension on the factory harness.

How it compares

Measured against everything we stock in Car Audio Accessories & Wiring, at today’s prices. Recalculated every night.

Price $12.99
Cheaper than about 86% of the 2,768 comparable items (median $21.99).

Specifications

Product
Brand nameMetra
Product typeInstallation Tools
Size & build
Overall height0.5 in (1.27 cm)
Overall width2 in (5.08 cm)
Overall length15 in (38.1 cm)
Product weight0.07 lb (0.03 kg)

Questions about this item

What factory antenna cable does the 40-GM18 connect to an aftermarket radio?

The adapter plugs into the GM vehicle's original antenna lead and presents a standard aftermarket radio antenna jack for the new head unit.

Will the short 15.00-inch length reach from my dash opening to the factory cable behind it?

At 15.00 inches long the pigtail spans most dash-to-harness gaps; if the factory plug sits farther back you can add a standard antenna extension cable.

How do I confirm the 40-GM18 is seated correctly after installation?

Turn the ignition on, tune the radio to a known local station and verify clear reception without static or signal drop-out.

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