I think I am in the second to last mission. Riding in a tank in a convoy. When we reach a certain spot some kind of droid is on a bridge...I blast away with cannon. Every time the droid flips a truck on top of us...we're dead. I have tried to beat this but, no success. (Have restarted this level at least 20 times). Any help would be appreciated.

Are you using both kids of weapons on that vehicle as one shoots the crappy little cannon and the other shoots the rockets just use a mix and get them killed even the pinger only takes 3 rockets loads for it to die from that section.

I had trouble with this at first until I realised the tank has TWO weapons!

My advice, button bash left-click AND right-click to use the turret and missile launchers, the missiles work wonders!