As John 250 wrote, the connection of the tounge is the first place to start, usually you can tighten that up a bit and often that will get loose again. Check the toe on the tie rods, you can toe it in more than you are supposed to on a worn out gear and that will make them track better. If you have a really worn out gear and have to travel very far and it is necessary to put new tie rods and tires on it, you might want to consider just buying a new gear, they really are not that much. I had several old ones that really just finally not worth putting anymore money into, but I do travel on roads a lot and the older ones were not worth the liability and buying new parts for. Heck just to re-bearing and re-tire an old wagon you can easily be into $400. A new gear is about $1200 with wheels and tires and that is one that will go as fast as you want. Sorry about so lengthy, just giving you some info. so you can make a informed decision, I have just seen a lot of my buddies put way too much money into old gears that still don't work good.