On my 83 Wagon (4wd, auto) I noticed a humming from the rear end that changes with speed.  I pulled the drums off each side and cleaned them up, bearings looked ok and didnt make any obvious noises.  Brake shoes were in great shape as well.

As I said, the hum changes with speed.  It does not change by turning or by pressing or releasing the throttle.  I changed the gear oil in the rear end and maybe it is a little quieter but I could be imaging it.  

This normal?

Noise is not normal.  Failing universal joints can cause this kind of noise.   Check them first.  

Wheel bearings can make a noise, but you can't tell condition by looking - unless you took the bearings apart.  If the axle nuts were tight, and the seals were good, they are probably ok.

I’m putting money on wheel bearings. The cv shafts shouldn’t be giving you any trouble since they’re generally ever used - if you don’t fit into this category, then they could be a possibility. 

Cheers 

Bennie

CV  axles look fine.  I agree its probably wheel bearings I am just surprised because ever bad bearing I have had has made more of a griniding noise and mostly when turning.

Bad bearings certainly can have a whining noise to them! It’ll even change noise with bumps in the road. 

Cheers 

Bennie

Its not really a whining noise.  Its more like a very low hum.  Sounds kind of like a straight cut gear mesh.

I agree with the U joint diagnosis.  Had a speed related hum on my '83 some years back, and my Subaru guru at Norm's Auto Repair in South Tahoe replaced them.  No more hum.  That was about 100,000 miles ago, at 292,000 miles.

I'm going to check that on the weekend.  I hope that's it, i have the tools to press in/out the joints.

The u joints are staked.  I had a local drive shaft shop rebuild one of mine, so I know it can be done.

9 hours ago, DaveT said:

The u joints are staked.  I had a local drive shaft shop rebuild one of mine, so I know it can be done.

Not on an ‘83. They’re replaceable. At least they are in Oz right up to the last brumby run in ‘91. 

L series, totally staked. Machining required to convert to replaceable uni joint yokes. 

Cheers 

Bennie

Interesting.   Well, that's a good thing, makes it easier to repair.