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Garmin GTX 327 Transponder Replacement
- Thread starter Robb
- Start date
You will have to do some wiring but the closest to that might be a 330ES
Are you ‘married’ to Garmin? Both Dynon and GRT EFIS units can control a remote mounted Trig TT22 mode S transponder (the Dynon transponder is a re-branded TT22). The TT 22 can ‘read’ the data from Garmin TSO’d gps boxes, and is remote-mounted - no panel space needed. If you want a panel control box, it fits in a 2 1/4” hole. Trig also makes the TT31 rack mounted transponder. Sized to replace King KT76, I don’t know the dimensions. Finally, Trig just announced a TT23, upgraded TT22, which I know nothing about.
I have two older GRT Horizon WS units I'm not sure if they will work
The GTX 335 or 345 is the same size panel opening but a bit longer than the 327.
Rack and wiring is not the same (recommend buying the optional GAE encoder which eliminates current encoder and wiring).
The 335 is out only and 345 is ADS-B in/out. They can be had with or without internal GPS.
You can also keep your GTX-327 if you install a Garmin GDL-82 in-line with your transponder antenna cable for your ADS-B-Out UAT solution. And, you can also use a Garmin GDL-50R for an ADS-B-In combined UAT / ES receiver solution. Even though Garmin no longer makes the GDL-82, someone is always selling a GDL-82 up on Ebay at any given time (4-units up there right now on Ebay). Otherwise, if you need or want ES for your ADS-B-Out, then you probably need to mount another tray and rewire a cable for something more like a GTX-345. I use the GDL-82 (Out) and GDL-37 (older version of the GDL-50R) solutions myself, and it's been working perfectly since 2019.
I think you need at least a 2010 Hx to get the remote transponder control….
GTX335 WAAS.
In my SeaRey, I swapped in a GTX-335 with a built-in certified GPS position source in place of a 327 to comply with the ADSB mandate.
As Walt says above, it is not a direct 1:1 swap, but I don’t remember having to re-pin more than 3-4 wires for a VFR-only aircraft built around an AF-5500. The only thing I remember having to add was a battery bus power (keepalive) so the GPS would align faster.
I mounted a GPS antenna under the fiberglass nose, used my existing transponder antenna, and it just worked. Since my panel didn’t have a WAAS GPS of any kind, the integral position source made a lot of sense.
As Walt says above, it is not a direct 1:1 swap, but I don’t remember having to re-pin more than 3-4 wires for a VFR-only aircraft built around an AF-5500. The only thing I remember having to add was a battery bus power (keepalive) so the GPS would align faster.
I mounted a GPS antenna under the fiberglass nose, used my existing transponder antenna, and it just worked. Since my panel didn’t have a WAAS GPS of any kind, the integral position source made a lot of sense.
That is what I do in my -8: Garmin GTX-327 transponder and a Garmin GDL-82 for ADSB-out (UAT 978). The GDL-82 also allows you to use the transponder in anonymous mode to mask your aircraft ID. I already had a 327 when I did my panel upgrade so I just kept it and got a GDL-82 from someone here on the forum.
