You cn run really high gearing ona TL01 provided You let the car cool down.

The motors can overheat if they are subject to too higher gearing, but people often mess around with changing the wheels on them too (I know I did).

You can't fit a heatsink with fan to a TL01 because you would cover the end bell, risking a short circuit. The heatsink I suggested is the biggest available and well worth the investment.

Chris