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Metra 40-GM21 Antenna Adapter

Works with select 1987-up General Motors vehicles — factory male to female Motorola antenna connector

Item # 12040GM21

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Item # 12040GM21

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About the Metra 40-GM21 Antenna Adapter

Metra 40-GM21 adapter

The Metra 40-GM21 adapter lets you connect an aftermarket antenna cable to the factory radio. It has a female Motorola plug on one end and a right angled male GM antenna plug on the other. This adapter can also be used when installing a wired FM modulator with the factory radio. Please enter your vehicle information or call an Advisor at 1-888-955-6000 to find out if this adapter is compatible with your vehicle. Warranty: 60 days.

What's in the box:

  • 6.438" antenna adapter cable (one end terminating in a female Motorola plug and the other end terminating in a right angled male GM antenna plug).
MFR #40-GM21

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More details on the Metra 40-GM21 Antenna Adapter

Product Research


Compatibility: 1987 and later GM factory radio with mini connector to universal antenna adapter cable (factory radio to universal antenna)

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Customer Q&A

Crutchfield asked: Why did you buy this?
Adapting factory radio to aftermarket antenna [ Ray  Jul 23, 2019 ]
I bought an isimple radio module to tap into my FM radio so that I could install an accessory audio input. It has Motorola male & female connections. I bought an oem female to Motorola male adapter for the connection between the antenna and module and a Motorola female to oem male adapter for the connection between the module and the oem radio. [ Charles  Feb 21, 2019 ]
Because your website recommended it and said I needed it to use the FM modulation Blue tooth adapter. [ Cory  Feb 09, 2019 ]
To install the FM Direct Adapter to my 1998 Pontiac GP GTP with factory AM- FM CD Radio [ George  Jun 14, 2018 ]
I needed it for my truck [ Jason  Jun 05, 2018 ]
Received an e-mail from Crutchfield letting me know I would need this with my previous order. [ Brian  Mar 25, 2018 ]
Need it [ Rebecca  Mar 04, 2018 ]
suggested with another part [ Amanda  Feb 23, 2018 ]
need it [ DAVID A  Dec 16, 2017 ]
always has had good service and quality material from crutchfield. Why shop anywhere else? [ Doyle W.  Jun 21, 2017 ]
Fits my truck [ phillip  Aug 14, 2016 ]
My goal is to add an AUX port to the factory installed stereo system. This item is one of two items needed to complete this goal in my 2005 Pontiac G6 GT. [ Paul  Jul 29, 2016 ]
I choose one but both showed up on the order. If I don't need both delete whichever one is not needed. Thanks John [ Tech Brown  Jun 12, 2016 ]
price [ ronald  Jan 12, 2016 ]

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