So glad you are changing bits! I hate TT's. Something else you may want to think about........he may not be very tolorant of a single jointed mouthpiece. Do you usually ride with contact or loose reins? A single jointed mouthpiece isn't really ideal for contact because it creates a nutcracker effect that pokes them in the roof of the mouth and it collapses on the tongue and bars. Some horses will toss their heads, chew on the bit, open their mouths, etc. if ridden in a single jointed snaffle. So maybe, if this behavior continues, get a double jointed snaffle, like the french link. You might also want to educate yourself on Myler's philosophy on bits regarding tongue/bar contact and relief if you aren't familiar with it already.
I actually would not ride him in the martingale. Something is triggering his behavior and really the martingale will just hide it. Find the cause and fix it, don't cover it up.