I appreciate the input , it is close but not touching. But if thing is really vibrating I guess it’s possible for it to touch in flight. I’ll put a dab of hot glue to ensure it doesn’t.
I have considered rotating the unit 180 degrees but haven’t because it make it difficult to access the pins .

For that reason , even though everything in the tail checks out , I did go ahead install a brand new tail boom and the entire tail mechanism from my spare tb40 kit , including different tail blades . It had zero improvement.
I did not try replacing the belt or belt drive pulleys , but they look great and they show no vibration when tested on the bench when the main and tail grip are removed.
I was also wondering if the tail belt was slapping around inside the boom , but with many different belt tensions there was no change . And I think it would have shown vibrations on the bench . That’s why I was curious on the unit mounting position causing the issue .
Maybe I should try a different belt and pulleys just to rule it out …

The problem could occur even because of wrong belt tension with some models. I understand it is very frustrating, because it could be really out of your control to make it smooth even with new parts. With some models you will almost never get resonant vibrations, some are very prone to this. But the source is always tail mechanics. In some cases when there is play at the tail hub even using a paper between boom (removing play with it) can completely fix the problem. So it could end up like a magic.

In any case if you are out of options and want to exclude a problem with your GT, then you can easily swap units from your second model (it is enough to save settings files and load it to other unit). The vibration readings should be identical with the same model.
The last possibility that could eventually cause so big readings is loose PCB (electronics) inside the Spirit enclosure. But this should not happen unless the unit was not opened and screws remained loose.

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Spirit System developer

Zex,
Once again I really appreciate you taking the time to respond and try to help guide me through this issue .
I have another spirit GT that I have yet to install, so I took that one and temporarily installed it and it had virtually the same reading on the vibration analyzer as the one installed on the helicopter, so I think that would rule out a loose pcb .

At this point I have taken apart , swapped out with new , double checked, tweaked , messaged and polished every piece of this helicopter , resulting in at best a slight improvement in vibrations shown on the y axis . There is simply nothing left to do . These vibrations have to be normal for this helicopter, albeit in an abnormal range .
At this point I don’t see what else I can do other than to fly it .
It flies great , and rescue has worked every single time I’ve tested it since the incident, probably over 50 times testing by now .
The only logical explanation I can come up with for why this happened was a glitch causing the unit to put in negative pitch instead of positive when I set the hard deck on the rescue auto that one time . And that was possibly a result of the intrinsic high vibrations in the TB40 .
I will be ready to switch the rescue off from now on when I set the hard deck .
Fingers crossed it continues to behave going forward.

Final numbers :
Bench test Y axis with tail blades on = 130 total
In flight test Y axis = 185 total
Vibration as shown in the data logger = 20-27%

While better than I started with , still considered extreme vibration on the Y axis , and in the normal range at under 30% on the data logger , according to the spirit software.