I have a 1968 220D automatic tran. which I am trying to get into safe order for in-town trips. I don't know the mileage on the car because the odometer is broken. The car has an odd characteristic which I am hoping to get your advice on:

With the rear end of the car on jack stands, if you put it into drive, only the left wheel turns. Now, before you call me an idiot, let me explain a bit more. While in drive, it is nearly impossible to stop the left wheel to get power over to the right wheel. I almost knocked the car off the jack stands trying to wedge the left wheel and get it to stop. Eventually, with great effort, I was able to stop the left wheel, in which case the right wheel does in fact turn. But it takes some effort to keep the left wheel still. And as soon as you let go, it starts spinning and the right wheel stops. Is this normal? Is this a safety issue? Maybe this is how all differential works, but it seemed odd to me. I am not very experienced with all of this, so any advice you can provide is appreciated.