Triumph Repair: 78 Spitfire Differential Noise, flange bearing, ring and pinion gear

Question
Howard,
My 1978 Spitfire 1500 has a noise in the rear end that we can not locate.  It is a rattle or tapping noise that does not occur under load, acceleration, or heavy braking.  It only occurs during coasting or crusing slow not under load.  The speed of the tapping is relevant to the speed of the vehicle, not the transmission gear, engine rpm, or anything else.  We thought it was U-joints, but they seem to be good.  Today, with the rear end off the ground, and the transmission in gear, I was able to turn the rear wheels fairly easily without turning the drive shaft.  A friend of my does not think that is normal, and believes it may indicate a problem with the rear end.  I don't know what to look at or check next, but would highly value any input you might be able to give me.
Thanks for your time.

Answer
Hi Brian,
I can't tell you from here where your noise is but if you are sure it is wheel speed then that eliminates the driveshaft and the ring and pinion gear and spider gears and narrows it to wheel bearings or axle "U" joint or even a rear brake part contacting a drum. Don't rule out a wheel itself. If it will also make the noise on stands or on a lift you can rule out a wheel so that would narrow it to wheel bearing, axle "U" joint or differential flange bearing or brake part.
If it will make the noise on a lift you should be able to isolate the noise with a mechanics stethoscope.
Howard