Hi,
I'm new to the hobby of RC and have purchased a few tanks to get started HL the Tamyia's are expensive and down the road I hope to pick one up. I did buy to HL tanks airsoft Tiger I and Pershing. they where cheap I paided 42.00 each I know they have plastic gears I'm sure haven't opened it up yet a little nervious about maybe breaking it. In soft dirt I noticed it slips and makes a gridding kind of noitce like gears slipping hard to explain I guess those experience folks know what I'm trying to say. I bought these tanks to learn and to work on them so do I have to upgrade the gears to get rid of this slipping? If so what type of gear and what else should I upgrade while it's apart. Thanks 
John