Thanx for the aid Emil.
YEP! I had mega problems with that worm drive, tried many different esc's to correct the problem, but couldn't.
A german friend set me up with a direct mount planetary gearhead motor and that solved all my problems. It's been working perfectly ever since. The only downside is that I had to hack up the body to get the body to sit flush with the floor as the vertical ghmotor is too tall.
I sent him a mail to see what he can do for you.