I feel your pain... I struggled with a CV axle seal on my GX 470 for over a year, trying different things. Here is what finally worked for me:
The final solution was to use 80W90 instead of 75W90. If you read the Service Manual for the 05 GX 470 it says to use 75W90 for the transfer case and 80W90 for the front and rear diffs. When I had the leak, I was using 75W90 and after I switched to 80W90, with everything else the same, the leak is gone. Some other things I did that were also important: seat the seal using the Wit's End tool, clean up the inside of the seal mating surface with a brass brush (lots of corrosion on mine), goop up the spring inside the seal with thick grease before inserting the seal so it doesn't pop off when you put the axle in.