Too much weight?

[fordmerc7]

My '29 Town Sedan suddenly got wobbly steering when I put 3 adults in the rear seat and one in front. There has never been a problem before or since. (I terminated the "tour" for my guests at the end of the driveway - but later the car drove perfectly well without them).
Can too much weight in the rear seat change the balance sufficiently to bring out a minor misalignment of the front end? -it was scary!