Uneven N/S wheel rotation. Differential? Half shaft? Bearings?

[Morgana]

With this wheel jacked up and the brakes backed right off, rotating it is easy until one point in the rotation where it becomes very stiff, but slightly springy rather than graunchy. The best way I can think to describe it is as if the wheel were connected to a cog and this cog were driving a teardrop cog. Straightforward on the circular bit, then harder up to the point, then easy again down the other side. The vertical link can be seen to move slightly while rotating the wheel over this 'hump', as if it's being forced backwards. Spinning the hub fast up to the point of strain leads to the rotation stopping and bouncing back with a bit of a clonk.

My first thought was a bent half shaft, but a straight edge along it at various points of rotation appears to rule this out. It is the same with the brake drum on or off.

The offside rotates smoothly back and forth.

Nothing untoward has been noticed while driving; the universal joints have been recently replaced both sides, and the reason I took the nearside wheel off in the first place was because a rattle over bumps made me think the shock absorber had gone.

[johny]

It does sound like a bent half shaft and I wonder if it would be possible to separate it from the diff and then rotate the hub to see how much the shaft wanders.... 

[dannyb]

I had this many years ago when I found the shaft was bent after removing the hub without the correct puller..

Danny

[Pete Lewis]

you can often see the rear trunion flexing around as you rotate a bent shaft 

Pete

[Morgana]

Thank you.

It is possible to remove the flange bolts without taking the whole assembly off, so @johny's suggestion might be the first port of call. If the differential side of the flange junction could be smoothly rotated by hand then that would rule out something rather more expensive...

[johny]

The flanges can be separated ok but you'll have to get creative to keep them apart as the spring tension tends to hold them together - jack a little under the vertical link?

[Morgana]

With the flanges separated it was a bit dodgy trying to support the vertical links against the spring pressure, so I took the whole thing out as if replacing the UJ. Thankfully, the differential flange rotates smoothly with no binding, so it must be something to do with the half-shaft end of things. Rotating it by hand doesn't show any major wobble, but as it's hard to keep still further investigation will have to wait on a big vice and the workbench to hold it still.

[Morgana]

More excitement today. With the half-shaft assembly off, there was no wobble outside a few thou with a dial gauge. However, we noticed the yoke could only flop one side a small amount, with full travel the other way. It turns out the plugged grease point, which bulges up out of the casting at the centre of the spider, was fouling the yoke. This is concerning as I followed Mr Haynes's instructions on this. "NOTE: The spider must always be fitted so the lubricating plug holes are towards the propeller shaft." Actually, it's clear that if the lubricating plug hole is positioned towards the hub end of things, the yoke is much deeper there and cannot foul.

Dismantling it again, reassembling in a helpful family member's fly press and regreasing (a couple of wear marks are the worst that the spider or needles showed) I am hopeful that the binding was nothing more than the greasing point rubbing the yoke. Possibly it only happened in the wheel-droop situation of axle stands under the chassis when the UJ was significantly cranked, so had no effect in use.

I'll put it back together tomorrow and see. If it's sorted, it's on to whether the shock absorber is crock or not.

[Pete Lewis]

one reason many uj are sold with a grub screw to blank the greaser hole 

and mr haynes is probably talking prop shafts not drive shafts 

there have been many a Tee shirt for fitting them back to front youre not alone 

Pete

[Pete Lewis]

and to add  you wont get a grease gun on the std nipple  it needs removing and fit an extended one just to get the gun on

so you dont want a greaser  its going to be useless 

Pete