To break in the gearbox I ran the motors with no load attached (both sprocket and tracks were removed) and ran the tank for 45 minutes on just forward drive. I did not put any grease on the gears. This also breaks in the motors. Afterwards I removed and recharged the batteries and ran the gears for another 45 minutes on reverse. I repeated the steps another 2 times and cleaned the lower hull of the sparkling brass and steel powder that have formed during the process.
I then started lubing the gears.After this I ran the tank with everything attached and just played with the tank on level ground while looking for any issues. For the first few runs everything seemed fine until the left gearbox began to seize and finally stop completely. I ran my fingers on the gears and tried pushing on the gears but they would not budge.
Seems like a few mato gearbox owners have had this problem. (see link. http://www.rcuniverse.com/forum/m_10699519/tm.htm) I had exactly the same issue with mine. Mato uses 2 different materials for its gearbox, brass for the gear and steel? for the the gear shaft. Since the 2 metal expands and contract under heat at different rates there is a tendency for the shaft and the gear to bind together and not move freely. In fact when I dissembled the gearbox (and I was forced to do this several times to fix all the issues) I could not even pry the gear from the shaft without tapping the shaft out with some force.
My conclusion was that the gear hole for the shaft was a bit too small that it was binding/seizing to the shaft. Here breaking-in the gearbox was of no use since once they bind the motor itself does not have enough torque to make them spin again.
My solution was to speed up the wear process by enlarging the gear hole a bit using a drill. I then lubed the inside of the hole and reinserted the shaft. That ultimately fixed the issue with the left gearbox. Unfortunately I forgot to take a pic of this step but as you can see later, this is the same solution I used for problem no. 2 I encountered for the right gearbox.
After re-installing everything and playing with the tank for several days I thought everything was dandy. However the right gearbox started acting up. It was turning slower than the left and I could tell the right motor was getting hot under the strain. Also the gearbox housing was hot to the touch compared to the left which indicated excessive friction was going on in the right gearbox as the gears turned.
When running the right gearbox I noticed several of the bushings were not turning on their mounts. After I disassembled the right gearbox, I discovered the bushing was actually sticking to the mount holes at an angle. The bushing itself was straight but it seems the mount hole was not only a bit small but is at a crooked angle. I drew the diagram below to illustrate. (the arrows point at the friction causing the shaft to stick and not turn)
Once I knew the cause of the problem the fix was fairly easy. Like the gearbox hole, I drilled the mount hole to enlarge it and basically straighten it out. The bushings now sit pretty loose in the mount holes and spin freely.
