front diff fill level
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Senior User
Joined: Oct 2004
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front diff fill level
Today I went to pull the fill plug on my front differential (99 4x4 SCab) to add some Lucas additive to the diff fluid and to my surprise I got covered with diff fluid when I pulled the plug. It was obviously filled way above the fill plug. This got me wondering two things, 1. The fluid in the front (or rear) differential should not be above the filler plug, right? and 2. How in the world did the previous owner, or service technician, get that much fluid inside this thing without parking it nose up on a huge incline? If anybody has any input on this let me know.
Lead Driver
Joined: Jul 2003
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From: Wheatland, Mo
Your knowledge is that same as mine..to the edge of the fill hole. The only way I can think of filling it beyond that would be to just jam the fill tube against the hole til it started to spit out then put the plug on real fast.
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I believe that Ford recommends that the fill level should be a fraction of an inch lower than the fill plug. Naturally, I can't recall the exact depth at the moment. If the diff fluid was warm or hot when you pulled the plug, thermal expansion of the fluid would have caused the problem you experienced. If it was overfilled cold somehow, thermal expansion should have blown fluid out the vent hose located on the passenger side of the axle.
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Now that you mention it Racerguy, it was milky looking. If there was water in it I'm sure that's a bad thing, right? Probably oughta drain it and refill. What exactly do I put in a differential, never had to do this before. Any help would be appreciated. Also, any ideas on how water would get in there?
Last edited by truckalpers; Dec 1, 2004 at 01:32 AM.
Hotshot
Joined: Aug 2002
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From: BC, Canada
Yes if there is water in there you should change the oil. Even if there isn't water in it the oil should still be changed once in a while.
It takes 80W90 gear oil, approximately 2 qts.
Water can get in through the vent hose if you did some deep water driving.
It takes 80W90 gear oil, approximately 2 qts.
Water can get in through the vent hose if you did some deep water driving.
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Thanks Racerguy, by the way, how critical is this situation? I'm getting ready for finals right now (Texas Tech University) and don't exactly have time to change it. I can make time though if you recommend that it be changed immediately. If I let it go, say, a week am I going to burn up the gears in there? Also, is there such a thing as a limited slip front diff? And if so, how do I tell if I have it.
Thanks
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Fleet Mechanic
Joined: Oct 2004
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From: Simpsonville, KY
Wouldn't it be a very bad thing to have a limited slip front diff? Don't those gears need to slip just a tad so you can turn?
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Hotshot
Joined: Aug 2002
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From: BC, Canada
If there is water in the diff it's probably been there a while now so another week shouldn't hurt. Water in a diff is never good but quite often won't do any damage as long as it's not left too long.
You don't have a limited slip front diff unless someone installed it.
It makes steering very hard. Been there done that, had the broken axle u-joints to prove it
You don't have a limited slip front diff unless someone installed it.
It makes steering very hard. Been there done that, had the broken axle u-joints to prove it