gear oil coming out of front vent tube
 

Hey guys. Got home from work this morning and went outside a little later and found a puddle of gear oil leaking out of the front diff on the my 97 Expedition. It appears to have come out of the front vent tube. I changed the gear oil in both of the axles last week and put in Mobil1 synthetic. No leaking until today. Possible I just overfilled it or should I start worrying now? lol I'm taking it on vacation in a few weeks (around 1500 miles) so need to have everything 100%.

Sounds like the vent tube is doing its job. If overfilled and the heat generated by running down the road, a little expansion is normal and what that vent is for. There are cases of "critters" plugging these up and creating enough back pressure to blow wheel seals.
I would just monitor, knowing if overfilled, will purge the excess and stop puking shortly.

Sounds to me like you overfilled it.

Thanks guys. Never had that happen before in any vehicle so it kind of worried me. I'll be racking up some miles in the next few days so I'll keep an eye on it and make sure it's not letting any more out then check the level.

Drove it to work today and there is a good sized little puddle under the vent. Probably about 4-5" in diameter. Also some dripping off the lower control arm. Also appears to be leaking when going down the road as there's some gear oil on the trans crossmember and other places underneath. It didn't leak before I changed it- or at least if it did it wasn't enough to leave any on the ground. Also I put synthetic in it when I changed it- 75/140 Mobil1. Not sure what was in there before. Going to have a small exhaust leak fixed tomorrow so it will be up on a lift and I'll check the fluid level then. I'm going to move the vent hose higher and see if it makes a difference.

I wouldn't expect that the gear oil wt will have much affect. With the access plug in the differential, it's pretty hard to overfill to get such a large pool of oil. Did you fill thru that plug or did you take off the speed sensor off and filled thru the top?

That's what I was thinking. Seemed like an awful lot of oil- and it's done it 3 times now. I filled it up through the fill plug on the front of the diff. It was just level with the fill plug. After searching around a while I found that there was a TSB on the 97's for blowing gear oil out of the vent.

97 8.8IFS - oil problem / questions - F150online Forums

Then some said even after the fix that didn't resolve the problem. I called the dealer for the updated axle tube and naturally it's discontinued. Found one online for $216 but I really don't have the $ to blow on it- especially if there's a chance it won't fix the problem. Would making some kind of a catch can be a good solution? Should be easy enough to do. Thanks for the help.

Found a picture online of the "fix".
F75Z-4K206-AA - Google Search

Looks like this is something I could do myself. Couldn't I just plug the current vent and drill and tap a hole in the location of the new vent? Would that be a better solution than building a catch can? If I'm losing this much gear oil driving 30 minutes @ 60 mph I'd hate to see what happens after driving about 700 miles @ 75 mph.

I can't imagine drilling into the axle well without removing the axle assembly first. Too much, especially if metal chips end up in the diff.
I would start with extending the vent hose, getting up higher and maybe add a loop in it at the same time. It will allow pressure to bubble up/out yet not allowing debris to enter.

Yes if I was going to drill into the axle tube I would definitely remove it first. I got a bunch of 9/32's hose at the store yesterday and extended the vent line to about 5 ft long. I had a little air filter sitting around so I put that on the end. Going to put new ball joints and tie rods in today so after that I'll take her for a drive. Checked the gear oil yesterday and I couldn't reach it with my finger so added about a pint to get it a little ways below the fill hole. Hopefully this will take care of it.

Well I won't know if the extended vent line solved the issue for a bit. Found out I need an oversize lower ball joint for the driver side :(. Ordered it today so it won't be here for 3-6 business days. Also I discovered in a moment of brilliance I ordered inner tie rods instead of outer's. Oh well I'll they'll all be new now anyway. Now I get to play the game of how long will it take the HOA to send me a letter for having a car on jackstands in my driveway :-X03

Just an update. I extended the breather line along the frame on the pass side up to the radiator. Put a T fitting in the hose on the frame rail and tied it into the hose up top so if it needed to vent it wouldn't blow gear oil out with the air. It didn't blow much out but still blew a little bit out. So next I took a bottle and ran the hose to it then tied it into the breather. Seems to work fine. Any overflow goes into the bottle then can drain back down into the line to the axle. Put about 600 miles on it today at 65-75 mph. Going to check the level on the front diff tomorrow but it shouldn't be leaking any.

Not trying to hijack the thread, but did you notice quite a bit of metal shavings in the IFS? I haven't changed it lately, but when I did years ago (switched all fluids to Mobil 1 synthetics) there was a ton in the front diff, very little in the rear. I chalked it up to the fact that the front diff works harder/has more wear and that the rear diff comes with synthetic from the factory. The front did not.

Based on what fact do you come to this conclusion?