Do not even THINK of the break in deal with Tamiya TU'S!!!!!!!! Oil all the gear shafts lightly (I use 10W-40), a spot of grease on each gear face, and run them...for years. The motors have internal suppressors. Plug and run, me lad. Periodic maintenance is the name of the game. Oil the TU's from time to time, and a spot of grease on the gear teeth.

While we're on that subject, suffice it to say I wince every time I see the 'break in' posts here. Valve lapping compound is a fine abrasive, designed to cut hardened steel and alloy valves. Some tooth pastes have fine abrasives in them also. Any time you are using an abrasive on your transmissions, the fine powder is getting not only on your gear teeth, but also on the gear shafts and bushings and 'breaking' them in also. Don't do it!! Take the new HL or Mato metal geared TU's, run them after a heavy oiling of the shafts and gear teeth for an hour in each direction and be done with it. You can NEVER get all the lapping compound out of your transmission with out special cleaners, and besides, the damage is already done.