Vibration while under way
 

I have had a slight vibration over this season that has progressively gotten worse. The last time we were out it got really bad. I shut it down and got back to the landing. I have so far pulled the drive and had it checked and it had no problems. The gimbal bearing looked good. The engine was 3/8" low in the front, so we have picked it up where it is completely level and aligned. The question I have do you think the 3/8" low would be enough to create the vibration? What other things could I check? I was thinking if the coupler could be on it's way out and has just no let go yet. The splines look good on the coupler.

I will be putting the drive back on tomorrow and taking it for a test run. To see if the alignment issue helped any.

Any luck