Hey guys just a quick question since transmissions are really not my forte and I'd like to avoid having to do any serious repairs in the future.

My 55 is a Ford-o-Matic car, and it had an empty transmission pan when we got her. It was a big issue for awhile trying to decide what fluid to fill it with since everyone online seems to say conflicting opinions on the issue. But that's not the issue, the car is up and running now and at this time I just have a general question.

Whenever I'm driving the car at normal highish speed say maybe around 40mph and I slow to a stop. If it's a relatively rapid stop, I'll notice right at the end when the car is about to come to a complete stop. I'll hear a somewhat subtle whirling sound and then a clunk as the transmission, I'm assuming, downshifts into 2nd.. I believe I've heard the first gear on those trannys is 2nd?

Anyway I'm just curious on weather or not this is normal operation or more importantly a normal sound. It's not a grinding sound of any kind just kind of a mechanical whirl and it's the only time I ever hear it is when slowing to a stop. I've heard that if you use certain tranny fluids it can cause "hard shifting" so I'm wondering if that's what it that is, or if I'm fine.

Thanks a lot for the info!