Rear Diff Fill, now leaking. Overfull?

[krispy97xlt]

All,

Last weekend I tackled the drive line maintenance on my 2001 Sport Trac 4x4.

I changed all the fluids from the front diff back to the rear diff.

I took a look under the truck a couple of days ago to check for leaks and found that my rear diff was leaking.

Upon a quick inspection it looks as though the leak is coming from the top of the diff near the fill plug, the oil is traveling down the diff housing and collecting on the bottom of the diff where if forms into droplets. Part of the oil is hitting the u-joint drive shaft area and slinging up and being thrown around.

I used ultra black RTV when putting on the diff cover, and waited about 1 hour after putting on the diff cover before filling.

When I filled I filled the diff all the way up to the fill plug with Royal Purple 75-140 with LSD additive (I have 4.10 LSD gearset). While filling the truck was resting on the ground, not lifted in any way.

I filled about 3 quarts of fluid. (Minus whatever I spilled and was left in the transfer pump).

I am considering pulling the diff cover and draining out this 6 day old fluid into a clean container so that I can refill to a proper level and reseal the diff cover (in case that is the source of my leak).

Does anyone have any pointers/ suggestions? Am I going down the right path?

*I know I sound cheap for wanting to reuse the rear diff oil, but that crap cost about $60 and I don't want to throw away good oil*

 

[corkey]

the fill plug is in the side of the diff just about pinion level,

that's it on the side, square hole,.

if you filled it into a hole higher up, there is too much in the diff, causing pressure when it warms up, making it leak, as it has nowhere to go,

 

[krispy97xlt]

the fill plug is in the side of the diff just about pinion level, that's it on the side, square hole,. if you filled it into a hole higher up, there is too much in the diff, causing pressure when it warms up, making it leak, as it has nowhere to go,

That axle is in an odd orientation, but there is only one fill plug and it is the one I used, removed plug with a 3/8 drive extension.

Usually I would expect the excess oil to come out of the vent, that wasn't the case on this leak.

Is the fill spec to be level with the full hole or some distance BELOW the fill hole? I have heard both.

 

[swshawaii]

Fill to 6 mm to 14 mm (1/4 inch to 9/16 inch) below bottom of filler plug hole.

Also recommend a few wraps of teflon tape on the fill plug threads after removing blue Loctite with a wire brush.

Page 235 #5
http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/01p27og6e.pdf

 

[krispy97xlt]

Also recommend a few wraps of teflon tape on the fill plug threads after removing blue Loctite with a wire brush.

Page 235 #5
http://www.fordservicecontent.com/Ford_Content/catalog/owner_guides/01p27og6e.pdf

Thank You. (Mahalo)


My first course of action was to remove some of the oil and re install the fill plug with teflon tape. I did that on Thursday PM.

Since then I have only moved it around the yard and pulled it into my garage .

I just parked the rear up on some ramps and gave a good cleaning to the whole diff with some simple green.

I have a space heater blowing warm air on it now in an effort to ensure all the degreaser has evaporated off of the diff itself.

Once it is dry I will take the truck out for a short drive around the neighborhood and then back to the garage.

I will check for fresh leaks and hopefully identify a source.

--> if a leak is found I will attempt to repair the leak source.
1. Cover seal
2. Pinion seal
3. Fill plug
4. ABS sensor

--> if a leak is not found I will remove the fill plug and verify fluid fill amount, and finally keep an eye on it to ensure no more leaking is happening.

It is entirely possible that I spilled a bunch of fluid on and around the diff while I was doing the first job and it has simply moved around since.

Any other ideas or tips?

 

[swshawaii]

As with ANY fluid check, you want the vehicle perfectly level. I've read a few that had the rear elevated have overfilled by over one quart. Although you didn't mention having an aftermarket 8.8 diffy cover, almost all that have inspection or fill plugs on the cover are at least 1" higher than the stock location. Also check the axle vent hose isn't plugged, spiders and bugs love open ended hoses for homes, including EVAP vent lines.

 

[krispy97xlt]

Final Update:

I waited for the cleaner to evaporate from the diff. Went for a test drive around the neighborhood ~2 miles. Came back and checked, No leak.

Went to run some errands around town, ~20 miles came back and checked, No leak.

Pulled the truck off the ramps and pulled the fill plug fluid is about "one half of a knuckle" away from the fill hole.

So all appears to be well.

I guess I am just a hypochondriac and a messy diff filler.

Thanks for the help! I will keep my eye on the diff for leaks in the coming weeks.