Hi
With the wife out I've jusk spent a lovly afternoon reading through the forum about torquetubes and leaks. I have a small leak at the diff-end of the driveshaft (a few drops over a few months) and somewhat more from the front. Does this mean that the diff-oil IS contaminated and MUST be changed? I have the torque-kit arriving next week, but have to do the work at a DIY garage. As such I need to prepare for (almost)the worst

I think you need to do a bit more to determine if that seal at the end of the driveshaft failed. The easiest way is to open the filler plug for the differential. If any fluid comes out inspect it for contamination by the tranny fluid. Since the tranny fluid is lighter than the rear axle fluid you should be able to see this contamination easily.
If no fluid comes out you may want to open the drain plug if you have one, or remove the lowest bolt holding the pumpkin to the differential and let some of that fluid out. Again , inspect for tranny fluid.

Good luck
JD

Thanks John for your answer.
To sum up:
Just change the oil
When all bolts are loosend its easier just to drain the diff and refill it.
Do you recommend a flushing or just a drain and refill?

Actually, I don't recommend changing the oil at all. I still have not changed the oil in my 56 and I've owned it since 1974. It has 129K on it now I think.

This will make some wonder about me and my motivation, but I do not advocate changing that which aint busted. Then again I am not in a restoration mode on any of my cars. I am in maintainence and refurbishment ( ie: fix what has to be fixed to keep it serviceable and safe.

That rear axle has heavy oil and I don't think it would ever need to be changed unless it is contaminated.