My truck is a 1977 f-150 4x4 stepside and learning about it every day.
Well I was down at the Woodward Dream Criuse yesterday and watching the show of cars when I noticed a wet spot on the ground inside left tire.I assumed brake fluid but it was gear lube leaking out where the u joint is.I just assumed it was an axle seal gone bad but to my surprise when I disasembled it there was no seal that seperates that drive axle shaft from the axle tube.I had topped off fluides a couple days before and filled the differential with gear lube up to the bottom of the fill plug.I removed some of the oil now but its still seaping out the area where the axle meets the tube.
Am I missing something here or is my front differential open to contaminants and water because of this design by ford?What if I drive the truck through a creek bed flooded roads or go mudding?Just doesnt seem right.

 

There is an inner axle seal thats probably bad you have to disassemble the axle take out both shafts and the ring gear with the carrier. On the inside there will be a seal for each side probably best just to replace them both while your at it. I just did mine but wasn't careful enough when I installed the passenger side axle shaft and it ripped the new seal so I'll be doing it again real soon. P.s. there are 2 different size seals so make sure you measure the diameter of the one you have

 

Bad axle tube seal. These are located on each side of the front differential. The diff carrier has come out to replace the seals.

 

Well that explains a few things I would think the diff would have to be sealed to the elements.Thank you very much gentlemen.Guess this would be a good time to install a detroit locker to.

 

a lot work for a $10 part. I need to do mine like yesterday.

 

Also keep in mind the direction the seal goes in, it's going to look backward to you because your sealing from the inside so be careful not to rip the seal when you install it as they are a real pain.