Differential noise

[Tom R]

I may be pushing the bounds of other projects, but I can't find any info on a rear differential and there seem to be some all round knowledgable people here.
I have a 109K junk yard rear end that I want to put on my Dodge Durango (the old one garbage), but after I pulled the drums off (yes they still used drums in 2000 ), I noticed a ratcheting noise from the differential and a slight notchy feel when I spun the axle. It acted like an open differential should as in one spins forward and one back, and it didn't seem to matter in sound or feel the direction or axle that I spun. It's fluids are full and it seems smooth when I turn the pinion shaft. Is this somewhat normal or did I get a lemon?

[SqDancerLynn1]

Since it is not in a vehicle I would pull the cover and the axles for a check of the Axel bearings .

[Agemax]

could be wrong but if turning the axle by hand, slowly, could the noise just be the gears in the diff taking up the backlash as is turns?

[Tom R]

could be wrong but if turning the axle by hand, slowly, could the noise just be the gears in the diff taking up the backlash as is turns?

I'm hoping this is the case. What I don't understand is: if this is the case, wouldn't it become smooth once the backlash is taken up? I've never turned a differential by hand before, perhaps it's normal.

[Agemax]

possibly turning it by hand slowly it is not constantly meshing the backlash, like it would being driven by the engine/trans applying constant torque on it?

[rustybronco]

Is this axle a conventional (open) rear axle or is it a locking type (clutch style) rear axle? Hold the pinion flange and turn one axle shaft. Does the other shaft turn the opposite direction or does it try to turn the pinion? If the shaft turns the opposite direction, the axle is an open rear end and the roughness when turning the axle shaft would not be normal and would indicate bad pinion and spider gears or, a bad axle shaft bearing.

If you can get another person to help by turning the other axle shaft the same rate as you turn your axle shaft and you still feel the roughness then look for bad axle shaft bearing, carrier bearings or pinion bearings.

Either way roughness is not a good sign of things to come. Ratcheting may be normal depending on if the center section is a clutch or a gear type 'posi-traction' axle. Either way, I'd be inclined to remove the cover (??) To inspect it if whom you bought it from will let you.

[gsgeezer]

You can always rebuild, then swap it out with the one on your truck, if you have any concerns.

[Sadsak]

When you rotate an axle in an "open" rear end and the other axle rotates in the opposite direction as you described, without the pinion rotating, you are driving the opposite axle through the pinion gears. These are coarse gears, usually with only five or six cogs. This results in a notchy feel but since this rotation is only present in the rear end during cornering, it isn't normally felt.
As was mentioned, since the axle is easily worked on out of the vehicle it would be easy enough to open it up and have a look. Personally, I wouldn't worry about it too much. Stuff it in and drive it.
PS: Cross your finger too. It can't hurt.

[Tom R]

I did have a look and noticed it was just as you described, just the courseness of the spider gears is all I was feeling. Everything looked nice and shiny with only a bit of metal dust on the magnet. It's been over two weeks and so far so good. I even towed my boat with it today.

[Sadsak]