Leaking Rear End

[eamici]

My son & I were trying to install the Differential using a jack and some cranking straps. After a while we were getting tired so decided to leave in hanging and try the next day. When we went back the next day to work on it, we noticed about a half a cup of pale green oily substance had leaked out. We didn't drop it or anything like that.

Anyone have any ideas as to why this would be leaking and/or offer some fixes?

The attached pic is a side view from the driver's side75582
Thanks

[edwardb]

Where was it leaking from? Can you tell? If left at an angle, very easily could drain out the axle holes if it's full of fluid. Those are open to the inside of the diff until sealed by the CV axles. Fluid could easily get by the tape it looks like you have there.

[eamici]

Its definitely at an angle. Unfortunately I may not be able to get back to it until the weekend. I can't ID the source of the leak at this time,
I'm presuming there is a way to replenish the fluid?

[Mountain-Metalworks]

I would 99.9% suspect that it's coming from the blue "plugs" used to seal up the diff for shipping like Edward mentioned. Those plugs aren't meant to be a tight solution, only keep dust/dirt out and most of the oil in. Once installed in the chassis, just open the fill plug and fill until it starts coming out the fill hole. If you're crazy anal you can drain the rest of what's in there, and refill with the correct Ford lube and friction modifier at the exact volume in the manual. It's pretty hard to overfill a diff though, they put the fill plug at a specific level so it spills out if you try to fill too much.

-TJ

[wareaglescott]

I'm presuming there is a way to replenish the fluid?

I would recommend draining it and replenishing regardless. I could never get a solid answer if it came all the way full or with just some fluid for shipping. The best answer I got from Ford contained the phrase " I think it is full". I was not willing to chance it. Very easy to drain and replenish once you have it on the car and the CV axles installed. EdwardB has the proper fluids and quantities listed in his build thread post #315.

Copied from EdwardB:
(2) quarts Motorcraft synthetic diff lube
(1) 4 ounce bottle Motorcraft friction modifier

[eamici]

Thanks again guys!

[Avalanche325]

Make sure it is not the main cover leaking. It is probably not. But, if it is, you want to fix it now.

There is a special gear oil form-a-gasket, I think by Permatex that I used on mine. Works great, no paper gasket. Yes, mine leaked right out of the box.

One other hint, if you need it. Buy the friction modifier on-line. At least near me, the Ford dealer was outrageous.

[jrcuz]

Just a tip if you do buy any of the Ford lubricant or friction modifier get it from Summit don't but it from a dealer it's about twice the price from a dealer ask me how I know.
JR

[CraigS]

Or skip the modifier. I always ran Mobil 1 gear oil in my solid axle w/ the Ford clutch type lim slip. It's GL5 which means it is rated for a lim slip. I run it now in my 2015 IRS diff also.

[eamici]

75873
How do get the fluid into the Diff. I see yellow plastic plug at about 1:00 if you can imagine the pumpkin as a clock. What do you use and eye dropper (joke). If you want to drain it, which plugs do you unscrew?

[phileas_fogg]

I used a squeeze pump (https://smile.amazon.com/gp/product/B000BQW5LK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) to get the fluid into the differential.

I don't think the yellow plastic plug is your fill hole. Rather, I think that's for a press-in fitting that connects to your differential vent hose.

On my differential, the fill port is at 4 o'clock on the differential cover. A standard 3/8" square drive is used to remove it. I know the differential is full when fluid comes out the fill hole.

To empty the differential, I loosened the cover and let it run out the bottom.


John

[jrcuz]

The yellow plug is where the diff vent attaches. it will need an aluminum barb fitting for the vent tube to push on to. For draining the diff remove the lowest threaded plug.
JR