I noticed that this cap is loose. I think its just a dust cap. Is that a cause for concern or does it not really matter?

 

mud and crap can easily get past one of those cheap little dust gaurds and into your dif. thats why some guys stick to the rocks and avoid the mud. when we pulled out my half shafts there was some dust and dirt in there. nothing alarming or bad, but it was there. if its loose it might be worth fixing. they are there for a reason. how loose is it? either way, id avoid the mud till you can get someone to check it out...

 

It moves back and forth about 1/2". Theres not anywhere it can really go. On the drivers side the cap doesent move but there is still like a 1/8" to 1/4" gap. So its not like its sealed tight or anything. Mud will get in there. Cap or no cap!