There are two forms of timecode, "file timecode" which is silent and contained in the metadata of the A/V or audio track, and LTC Audio timecode which is recorded as an audio sound, typically the L or R channel of one audio track.
Technically even two cameras with timecode connectors and jam sync ability use LTC audio on the wire to sync them. IOW if you connected that wire to a speaker you'd hear the familiar sound.
If your cameras were jam synced or manually set to time of day timecode, after importing to FCP you can skim the video and see the timecode value below the viewer. Each clip should show a rational timecode number that corresponds to the time of day for that shoot. That assumes View>Clip Skimming is enabled, and the camera was set to free run timecode, not restarting at 00:00 for each clip. If you skim the timeline (not the clip) it will show project timecode, not clip (aka source) timecode.
Audio recorders like the Sound Devices MixPre II series have a built-in timecode generator and can be jam-synced from another timecode-enabled camera or other timecode source. After that there is no audible timecode on any audio channel, as the recorder uses its internal timecode generator to record "file timecode" as metadata within the audio data.
The fact you can hear LTC audio timecode in the external audio implies there was an outboard timecode generator like Tentacle attached to one of the channels.
FCP cannot read LTC audio timecode, only file timecode. However you can use the free version of Resolve to read that audio data and insert it as file timecode. That can be exported as a WAV file and imported to FCP. The procedure is shown at 21:00 into this video "The History and Science of Timecode":
Once all A/V and audio clips have the proper file timecode, they can be synced in FCP when you create a multicam clip. You simply select "Use Custom Settings" in the create multicam dialog, de-select "use audio for synchronization", and for Angle Synchronization select "Timecode". However each batch of clips from Cam A, Cam B and audio should be first labeled in the Inspector>General View>Camera Name.
Thanks for the detailed reply - wow that's a big gotcha with Final Cut!
i spent 5 hours last night syncing the files manually- the painful legend of external recording of audio continues.
The sound guy wanted to record externally for maximum audio fidelity - and to keep access to 5 channels of audio in post.
Premiere also does not have sync on audio timecode (which actually works). If your audio is decent quality, FCP can normally sync on that. However if on-camera audio is turned off or poor quality, or if there are many short stop/start takes, audio sync may not work. Likewise if the camera and recorder time of day clocks are not set accurately, you cannot even roughly order the clips based on file creation date/time.
In some cases the 3rd party tool Plural Eyes can sync on audio better than FCP, but IMO that's not the ideal workflow. That said if there is lack of planning and execution during the production phase, sometimes Plural Eyes is an option: www.maxon.net/en/red-giant-complete/pluraleyes
Any camera or recorder which has free-run timecode and allows manual timecode preset can often be roughly synced before shooting -- without using audio timecode or file timecode. E.g, you set the first device to free run timecode, then set the time of day clock *and* preset timecode to the current time of day. You then hold up the 2nd/3rd/4th devices to the 1st and while viewing the free run timecode, manually preset it to that same value. You can normally get it within about 1/4 of a sec, which at least gets it close. Then then NLE can normally sync on that timecode. That said, timecode format for .mp4 containers is not universally standardized so some NLEs might not read that properly. More professional container formats like MXF normally handle timecode better and are more consistently handled by NLEs.
An efficient post production workflow requires planning and discipline during production -- even if using file timecode. If the cameras and recorder are not jam-synced properly and if the sync system is not well tested in advance, it will often cause greatly increased work in post -- no matter what NLE is used. Even if there is a Zaxcom timecode-referenced recorder on each device providing continuous file timecode, and if there is Zaxnet remote wireless timecode sync, if the personnel do not configure and test it properly then timecode sync in post will not work: www.gothamsound.com/product/zfr300-audio-recorder zaxcom.com/what-is-zaxnet/
An efficient post production workflow requires planning and discipline during production -- even if using file timecode. If the cameras and recorder are not jam-synced properly and if the sync system is not well tested in advance, it will often cause greatly increased work in post -- no matter what NLE is used.
This needs to be shouted from all the rooftops everywhere.