Shaft flutter- I tested my TC4 on the bench with full throttle, a huge 38 tooth 48 pitch pinion at full throttle. Nothing but smooth. No drive shaft wobble. I realize as the car ages this becomes a problem and even is a problem with new cars on a high speed open mod layout.
So why does mine not wobble.
First it is a new Aluminum shaft which have proven to be the straightests. I tried associated composite shafts previously and was not happy. I returned to aluminum.
My shaft has stayed straight in the crashes due to the slipper spool in front.
My drive cups are new. This is imprortant. The shaft should be a snug fit in the cup as you install it. Replace worn cups that let the shaft go off center.
my pinions are properly shimmed for low end play. This keeps the input shafts running more true.
My bearings are relatively new and have low slop.
Anyway this is not a problem for me yet.
I and the car continued to improve. I plumped up another battery with a long practice run. Time for some gear experiments.
I dropped four pinion teeth. The car lost some punch and top speed, but I was rewarded with faster laps. 10.5's in practice. .2 better than my best previous race lap. So why the improvement. I seemed to keep the corner speed higher on the very tight track when the car had less punch. I probably ran some 10.4's in the race. I am closer to the lead pack.
Anyway this alltime best way to adjust gears
once your lap times stabilize within a few tenths for each of many laps..
Change the gear
Check the lap time for the top five or top 3 laps.
Go more in that direction if times improve. Check your motor heat though.
Current gear with the 13.5 is 66/34 x 2.5 = 4.85
I broke C-hubs in the first and second heat. I went home for lack of sufficient spares.