i actually have one of these card, hsp flying fish, mines had a couple of upgrades, they usually come with locked rear diff or at least mine did (mines the flying fish 2), if they wont spin in opposite directions, then its locked already, seen ur posts about making it rwd only, and its a waste of time, iv tried it, spins far too easily even with little throttle on drift tyres, and even on some rubber road tyres i have, i went back to 4wd after about 5 mins with each set of tyres for testing, one thing to look at upgrading if you can is the front arms, they develop a rattle after time, iv fixed mine with spacers for a temp fix until i can order parts, and the plastic hex that sit into the wheels didnt last more than 5 mins when i upgraded to a brushless setup, ripped through them other than that, mine has withstood a bit of kerb bashing and been solid, watch out for the front bumper/body mount holder underneath the foam, i snapped mine, and they are very hard to find for less than about 20 quid, i just made a custom one cos again, im not ordering any parts for it yet, but yeh, its a pretty good beginner car