Classic/Antique Car Repair: rear differential noise, rate of acceleration, plymouth fury

Question
Thanks for the advice on the windows on my 65 plymouth Fury. I have a question about the rear. It makes noise when I drive,kind of a whine that gets louder when you go faster.I took off the tires, and noticed that I can move the axle a little up and down and in and out where the rim bolts on. Is that normal or is there something wrong with the bearings?Or could it be something else?Thanks.   Bill

Answer
Without hearing the noise myself, it's risky for me to guess, but you can sort through the possibilities by paying attention to whether the noise gets louder on a turn, and if so which direction you turn makes it get louder.  If a curve to the right makes the noise get louder, the axle bearing on the left side is bad, and vice versa.  

If that isn't happening to you, then notice if the rate of acceleration makes a difference in the noise. If you can make the noise disppear by playing with the accelerator so the engine isn't pulling at all, the noise is coming from the pinion bearing at the front of the differential.

See if that helps, and let me know.  There is always a tiny bit of play in the bearings - but you'll have to judge if it is excessive - if you can move the brake drum up and down more than 1/16th of an inch, that sounds like too much -and less would be better -but the first test I gave you should point out a bad bearing.

If none of those things seem to be the cause, it might be your tire treads - you could try swapping wheels with the front axle to see if it makes any difference.  Snow tires are famous for this sort of noise.

Good luck!

Dick