So I was under the truck to work on the exhaust, and I noticed this. I'm guessing the seal where the drive shaft goes in is bad. It's wet on the other side too, so I guess it needs a new gasket there as well. How big of a job will I be getting into to fix this?

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My 86 seems to periodically loosen up the nut so might just check that. I typically have been able to just snug it and go. I have had success simply taking the nut out then the yoke and do the seal. Is this fully proper? Maybe not, but I get away with it. Just have to make sure it is tight enough but not so much that it would start to drag if that is even possible with the design as some have crush sleeves set by torque to set the depth of contact into the ring gear.

That looks like a Dana axle. Some of them are set up with a hard spacer and shims to get the pinion depth and bearing preload correct. That setup is easier in that you don't have to worry about over tightening the pinion nut like you would if it had a crush sleeve.

Like Fellro said it's just taking off the pinion nut, removing the yoke then replacing the seal.

What I would add to that is mark the orientation of the drive shaft with the yoke before removing the drive shaft, that way you can get them on the same way it was before.

Also, before you remove the pinion nut, mark it along with the pinion shaft, and pinion so you can be sure they are oriented correctly when you go back together. Also be sure to count how many threads are visible between the nut and the end of the shaft so you get the right number of turns on the nut when going back together.

The other thing to check is whether a groove has been worn in the pinion where the seal contacts it. That might cause some leakage as well.

Good luck!

I also had to add a sleeve on the yoke shaft, since there was a groove worn in the shaft. Just replacing the seal didn't cure the leak.

Thanks for the tips. Most of it went over my head though to be honest, since I've never worked on a rear end and don't really know how it goes together or what the parts are called. My nephew lost my shop manual, so I'll have to order another one and read up on it.

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http://www.fordtruckfanatics.com/forum/forumdisplay.php?f=129

The ford truck manual(for a '78) is available on this website at the link above. Granted, you have a '77, but a lot of the mechanicals are the same.

fatherdoug said:

http://www.fordtruckfanatics.com/forum/forumdisplay.php?f=129

The ford truck manual(for a '78) is available on this website at the link above. Granted, you have a '77, but a lot of the mechanicals are the same.

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Ah, that will be super helpful. Thanks!

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