Last month I found that the left side rear end seal was leaking so I went ahead and replaced both rear end seals. I happen to glance under the truck today and the right side seal is now leaking, is this a common issue and what should I do now? Its a 99f150 with a 5spd manual 4wd if it matters.
Thanks!

 

You might have an axle or an axle bearing problem allowing the axle to move arouns and cause tha rear end grease to leak out. Look at the axle where the bearing rides and see if there are any grooves or pitting.

 

Thanks, ill take a look at it when I get back in town this weekend.