the 27mhz radio systems have always had problems it would be best to upgrade to a nicer 2.4ghz radio.
If you want to try and get a little more range without upgrading:
1:Make sure all transmitter batteries are fresh
2:Make sure anttenas on both the transmitter and reciever are extended all the way.
3:Make sure the "truggy" you said you're driving is on full charge.

Good Luck.