Karsons Front Swivel Housing Shim Kit

On the end of the axle are the round swivels where the bearing cups fit, these are rusted but welded as part of the axle, do I need to replace the axle to stop leaks?
Corrosion to these round swivels is very common on this Toyota setup unlike a LandRover for example where they unbolt off, the Toyota axle swivels seals are relatively crude as they are only designed to hold back hub grease and not oil like the LandRover, therefore, a good cleanup with some coarse emery and apply a thin smear of grease to the balls before assembling the swivel seals and the axle should be fine.

Why does oil run out onto the wheels?
The main hubs in the CV joint area etc are only filled with grease NOT oil or a form of liquid grease. The swivel hub seals behind the two half moon plates, felt, steel ring and the rubber flat seal are only designed to hold back grease, hence why the pitting or corrosion as mentioned earlier isn't such an issue.
When oil from the differential is allowed to flow into the hub then it contaminates the grease make a "liquid type" solution, the swivel seals not being designed to cope with this then allows the diff oil to flow out the bottom and onto the wheel.
So, a lot of the time it can be the small axle oil seal which seals the axle casing inside to the half shaft that "could" be allowing oil to seep past and into the hub contaminating the grease.

Remember, good mechanical advice is to always look for the reason for ANY failure and not just the obvious.....in this case obviously oil is running out past the round swivel seals but is it in fact the small axle seal that really causing the issue?....these are the question that you or the mechanic need to look out for else you could be doing the whole job again, another reason why this kit is great as it contains all the seals and bearings that you will need.

What do the shims do?
Shims on this axle setup do two things,

• Firstly they align the whole knuckle housing (The main casting that has the 4 large studs top and bottom), this is essential so that the half-shaft running from the differential into the hub runs central to the small axle seal. For example, if you fitted to many at the top and none at the bottom then this would, in theory, mean the knuckle runs to high and would force the half shaft up against the seal more at 12.00 o'clock, in time this would cause early oil seal failure and again the oil to seep past as mentioned earlier.
• The shims adjust the preload applied to swivel bearings. If you had no shims then you would over tighten the preload, too many and you would have slack bearings whereby the whole knuckle and hub would be loose. Again getting the preload correct is essential. 
  Toyota manual states preload of the swivel bearings, using a "Spring Tension gauge" (like a fisher man's weigh scales) to be:
  (When rotating) 3.0 - 6.0 kg (6.6 - 13.2 lb)