First Welcome to The Forum! Second I'm not sure at this point whether this is your first start your first car you've had a thousand of them and you know what you're doing or what? The first thing I would do right out of the gate is fix it myself! Synchros are $50 and a whole rebuild kit for that transmission is probably another hundred. The problem is too many people having just simply taking things apart and that's how simple it is there's no tolerances or anything crazy and if the one spot were a bunch of bearings fall out and they actually fall out that can be put back in with a piece of broomstick handle! But with that said how much money do you want to put into things that go to a /6 in this Dart?? I'm already scared the four speed you're looking at is actually the overdrive? And not a true 4-speed? If it is a true for Speed and NOT a 4 speed overdrive, I would grab that anyways if you can get it cheap. But think about how much you're putting into this car and how much you like the little rice burners to show you how it is out on the streets? That's what I thought, I don't think so? Quite honestly it's probably just one of the little fingers inside one of the gears that's worn out and making it pop out of gear. There's a $25 book you can buy at any bookstore any good book store that can show you how to rebuild almost any transmission with pictures! LOL
Don't be scared of your car unless you don't use jack stands! LOL
