Axle seals ‘99 F150

[melk]

1999 F150 5.4 2v 4x4

Bought from my neighbor 2 years ago, who was the original owner. Spent most of its life as a camper rig in the Southwest. No rust of concern, body and frame in great shape overall. Just lots of overdue maintenance needed, entire front end needs to be redone, front passenger hub is shot etc.

I let my son daily it for the last couple years as every American teen needs a truck as their first vehicle, right?

Anyhow he’s moved into something else and I took the truck back and am ready to start tackling the long list of repairs.

Climbed under the rear end to drain/fill the diff and found this lovely surprise waiting for me. It wasn’t like this when I bought it, but I don’t know how long it’s been like this either.

I’ve never done axle seals before but watching some videos it doesn’t seem too terrible really. Wouldn’t mind a little pep talk however or any general advice for the job. Thanks!

 

[bdcardinal]

Its not terrible. I think that is a 9.75 axle, but that tag on the cover bolt, not the ones that says "synthetic fluid only" the other one will either say 8.8 or 9.75 or I think there might have been a 10.5 option then but its hazy. You might also need the e-brake shoes if that is important to you. If on that tag is says 3L73 or 3L55, the L indicates it is a limited slip and you will need modifier or the fluid that has the modifier in it already. Looks like you are going to need a lot of brake cleaner too.

Also remember, step one after it is lifted is to loosen the fill plug on the diff. You don't want to be caught unable to fill it back up.

 

[crashz]

Its really not bad to do on a semi-floating axle. Be prepared to jump from the underneath the truck to each side a few times. Cleaning up the mess will probably be half the work. Also, get yourself a Lube Locker gasket for the rear, then you don't have to mess with RTV.

 

[melk]

Yep it’s a 9.75 LS rear 3.73 gears and 8.8 up front

Will definitely replace the parking brake shoes as well.

 

[MNgopher]

Did two of those on my '97 and '99 F150's. Honestly not too terrible of a job. As noted, make sure the fill plug isn't stuck before you start anything - not a good feeling to realize that after doing all the work! Also make sure you leave enough room to pull the axle shaft out where ever you set up to do the work. Let the RTV cure per the cure time if you go that route on resealing the diff cover.

 

[Ursatdx]

I recall, years ago, that the proper fluid level on some ford axles was 3/8" below the bottom of the fill plug.
Overfilling would cause axle seals to leak.
Just a thought.

 

[tblt44]

I had a real small leak AT 205 re-seal stopped mine

 

[D60]

If the shafts are grooved then you'll have to formulate a game plan. On the SF 14b "offset" seals abound. Never shopped for a 9.75.

You may want to just do the wheel bearings while you're at it. A good slide hammer and "toggle" puller are your friend.

 

[bdcardinal]

If the shafts are grooved then you'll have to formulate a game plan. On the SF 14b "offset" seals abound. Never shopped for a 9.75.

You may want to just do the wheel bearings while you're at it. A good slide hammer and "toggle" puller are your friend.

I just came back here to suggest new bearings. Also maybe spend some time cleaning and painting that cover, or get a new cover.

 

[D60]

I just came back here to suggest new bearings. Also maybe spend some time cleaning and painting that cover, or get a new cover.

Still, what with new parts these days I'd pony up for some better bearings. Probably BCA or SKF through RA. Also, not sure OEM -- if even available -- would be any better than those two. By now surely Motorcraft has been contracted out to a lesser manufacturer.

 

[bdcardinal]

Still, what with new parts these days I'd pony up for some better bearings. Probably BCA or SKF through RA. Also, not sure OEM -- if even available -- would be any better than those two. By now surely Motorcraft has been contracted out to a lesser manufacturer.

They should be Koyo.

 

[2strokeNorthstar]

I recall, years ago, that the proper fluid level on some ford axles was 3/8" below the bottom of the fill plug.
Overfilling would cause axle seals to leak.
Just a thought.

Not on the 9.75.
I wouldn't bother with bearings unless it was run low on oil for a while. It's a very basic rear differential to work on. To reseal use gear oil rated rtv, "the right stuff" or a lube locker gasket. I've never used a lube locker but they get good reviews. Regular RTV will eventually leak when using friction modifier gear lube.