I replaced the back left axle bearing and seal on my 99 f150 several months ago, but the seal is leaking again already. I checked the vent tube and it's clear, so I'm not sure why it's blown out. It was good for about two weeks and then I noticed the oil dripping again around the hub. It's the 3.55 non-LS and I used the synthetic 75w-140. Any suggestions as to why it would leak so soon?

 

Here's a few suggestions:
1. The seal you installed could it have been damaged during install?
2. On the axle shaft, where the old seal rode; did it have a small groove worn into it. If so, you can try and smooth it out with a fine grit sandpaper
3. Check and see if you installed the seal the right way. one side faces inward to the center of the axle.
4. When you go to put the new seal in, use some rtv around the outer edge of where the seal sits in the end of the axle tube. I forgot to use RTV on a pinion install. about 500 miles later, Hello leak!!
Hope this helps out some.

 

most likely damaged the seal upon install... I have done several and have NEVER leaked again...


knock it in with a soft hammer and lube it up when you install the axle... use the actual gear lube and smear it all around the axle and seal lip