2001 drive shaft seal

Sorry if this is posted in the wrong part of the forum. I need some help ASAP. I have a 2001 Prius which recently developed a leaky drive shaft seal (RH UK Drivers side). I replaced the seal and found the whole experience quite simple and straightforward BUT it was still leaking. I have pulled it all apart again and have a 2nd new seal but I am thinking if I put it all back together and nothing has really changed it will probably just leak again. I didn't damage the seal putting it in but I did push it a little (2-3mm )below the face of the trans housing. I read somewhere it has to be flush with the housing but I can see why it make any difference, I didn't cover the oil passages.
One thing I did notice is the seal seems quite loose on the shaft, it just seems to slide on too easily. The shaft seems fine but does have 2 lines where the seal sits, no ridges though.
Can anyone shed any light on what might be the problem, why a new seal would leak ? When I started the car and let it run for a moment the fluid was visible around the seal not just at the bottom.
Any help would be appreciated, thanks.

 

I suppose loose was the wrong word, it just doesn't seem tight enough to seal properly, perhaps they aren't very tight on the shaft ? Both were from the local Toyota dealership in Toyota bags with the correct part number so I think it is the correct seal. The issue is though why would a new seal leak and is there anything else that could cause it because I am out of ideas.

 

Thanks. I did do this before removing the shaft the first time and there was very little movement but I will replace the shaft tomorrow and try again.

 

Well my other post on this subject has disappeared which is a shame as there was an interesting reply. Apparently the fluid level should be below the seal which doesn't sound right as when I removed the shaft a couple of litres of fluid came out. My understanding is the level is checked by removing the fill plug. If that is the case then the fluid level is way higher than the seal. Confused now lol

 

Thanks, yes that's what I thought.

 

OK so no other thoughts or ideas guys ? Really don't know what to do for the best as everything seems fine.