Leaking rear axle seal

I have a 1988 2.3 Mustang with a rear axle seal that keeps blowing.  I bought the car new, and somehow, a repair bearing got put on the passenger side axle.  I don't remember ever having this done, so don't know if the dealership did it or what.  In any case, it won't stay sealed now, but it did for many years prior.

Is there some kind of vent on the axle housing that may have plugged up, allowing too much pressure to build up and blow it out?  If so, where is it, and can you get replacement ones?  

If seals keep leaking after replacement, it may be the axle itself is too worn to accept a seal. or the axle isn't being retained properly in the axial (in and out) direction.
As far as I know there typically is only one vent on the axle housing, if one seal leaks and the other doesn't it's pretty unlikely a pressurization issue.  

the axle vent tube could be clogged...

ford basic part number   4022  Axle Vent Tube

there are several slight variations depending on ring gear size...

7.5 or 8.8

single exhaust or dual...

according to the slightly later part info i looked up at motorcraft.com

if you are going to order one from ford... or even ask them.. be sure to take a picture of the ID tag on the rear cover bolts..  or write the numbers down from it..  

with the brake drum removed, how much play does the axle shaft have up and down, and front to back, too much play will not allow the seal to make contact, another thing when you install the seal did you prelube the lip where the axle go through, Assembly lube, grease, or diff oil? if not you may have just burnt the lip out, before the diff lube got to it.  

I have encountered offset bearing kits that are used when the bearing goes bad and scores the axle shaft. They offset the bearing to utilize an unused surface on the normally unserviceable axle. Normally, axle shafts get replaced when new bearings are installed on this type of rearend, bearings rolling directly on the axle, instead of an inner race. Is the seal riding on a smooth surface or a damaged surface? If it's rough, a new seal will not help.  

Yes, I used assembly lube, and yep, the surface is, or at least was, smooth.

Does anyone know where exactly the vent tube is located?  I want to see if it's rusted shut or clogged with grime.  

The rear axle in the photo is the 8.8 the vent is the little device shown on the upper right axle tube (or left side of the axle as viewed in the photo)
http://image.carcraft.com/f/techarticles/9256024++w569+h356+ar1/116_0705_02_z+ford_8.8_rear_end+comparison_with_chevy_12_bolt.jpg  

Thanks.  I think I found the vent, a tube-like structure attached to a bracket where 3 brake lines come together. The vent appears to be solid, with no opening or hose attached.  How is this thing supposed to vent and how do I remove and replace it?  

its a bolt that you can remove, that holding the flex hose to the axle, there is like a small beer bottle cap covering the top of it, it may have like a metal scrubby  pad through the center of the bolt..as a filter. try removing it and soaking in in thinner or the likes and blow it out..  

I'm going to try removing it over the holiday weekend.  In case I need one, does anyone know a source where I can get a replacement axle vent tube for this stock, 1988 2.3L Mustang or do they not make them?  I can find them for 64-73 Mustangs, but not Fox bodies.  

you do have an option.. since all the dealerships are probably closed this weekend..

that you just extend it with some single layer vacuum tubing..  radiator overflow tubing..

curl it into a triple loop and gently tie wrap it..  up high to the bottom of the car.. hanging down.. not flat against the bottom of the car..   hook up the end to your vent..  now you can use any breather..

i could not get a full ford part number to fit your application. but i was looking online. not calling the dealer ships..  the vents seem to be under 10 bucks for the ones i was able to price..

the ones on ford ranger 4x4s have the proper shape to hook the hose to ...  same ford basic part number... as above.. XXXX-4022-X