aFE Rear Diff - Post Install Question

Question for those who have installed a new rear diff cover on their truck, specifically a aFE one.

I did the swap in the driveway yesterday and it was relatively straight forward. Got everything cleaned out, cleaned the mating surface, and used some brake clean and rags to clean the old fluid entirely out.

In reading the instructions, it says that the capacity should be around 4.5 qts. So as I filled it, I got to 4qts and I was even with the little fill hole. At 4.25 qts, I have now covered the sight glass. So I'm not even reaching what the instructions say...

Is this normal? I thought the actual capacity was supposed to be 5 qts?

Swacer said:

Question for those who have installed a new rear diff cover on their truck, specifically a aFE one.

I did the swap in the driveway yesterday and it was relatively straight forward. Got everything cleaned out, cleaned the mating surface, and used some brake clean and rags to clean the old fluid entirely out.

In reading the instructions, it says that the capacity should be around 4.5 qts. So as I filled it, I got to 4qts and I was even with the little fill hole. At 4.25 qts, I have now covered the sight glass. So I'm not even reaching what the instructions say...

Is this normal? I thought the actual capacity was supposed to be 5 qts?

Click to expand...

Make sure it's level. Go give it a light drive around (park level) and check it.

I installed the same cover. I basically keep it covering the sight glass. It's not an exact science.

If it isn't totally level, it makes a big difference on the sight glass reading.

I do the same as Dane.
I actually have had to add the rest of the half quart over the past year and a half.
Now it's low again, and the fluid smells a little burnt. No leaks of any kind.
So I just ordered 5 quarts of Mobil 1 75W-140 Synthetic Gear Lube on Amazon.
And Transfer case fluid.

Thats interesting that you mention the fluid disappearing.

At 38k miles, when I opened the rear case, I found 1qt of fluid or less, and also found some metal shavings. Over the winter, when I would leave my house for work in the morning, the truck would make a "crunch" when making a left turn. Only would happen once, but would happen like clockwork every morning. The dealership claimed it had something to do with the E-brake, but i never quite bought that.

Now that i"ve seen how much fluid was in the rear, I know for sure what i was hearing was gears binding up due to a lack of fluid. I've never seen a diff that empty before...without being cracked.

Now with 4.25 qts in it, its quiet and smooth. I do plan to mention this to my ford dealer though and provide them with pictures I took so its on my file in case something happens to the rear end.

As for the comment on being level, my driveway is level, and it still shows full at 4.25qts. So I guess it will stay there for now.

Why not fill the diff to the threads of the original front fill plug? How does that compare to the cover sight glass?

I wonder what the instructions are to fill the rear with a stock cover.
I can only find total amount needed, not fill till it flows out of the fill plug, like the transfer case.

Swacer said:

Question for those who have installed a new rear diff cover on their truck, specifically a aFE one.



I did the swap in the driveway yesterday and it was relatively straight forward. Got everything cleaned out, cleaned the mating surface, and used some brake clean and rags to clean the old fluid entirely out.



In reading the instructions, it says that the capacity should be around 4.5 qts. So as I filled it, I got to 4qts and I was even with the little fill hole. At 4.25 qts, I have now covered the sight glass. So I'm not even reaching what the instructions say...



Is this normal? I thought the actual capacity was supposed to be 5 qts?

Click to expand...

Funny you posted this because I was going to check mine tonight.

When I had my aFE Cover installed, the installer told me the same thing as what you described above. I brought him 5 quarts of Amsoil and he could only put 4 quarts in it. Just keep an eye on it. That is the beauty of having the sight glass.


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MTF said:

I wonder what the instructions are to fill the rear with a stock cover.
I can only find total amount needed, not fill till it flows out of the fill plug, like the transfer case.

Click to expand...

When I checked the fluid level in the stock original fill plug hole before removing the stock cover, it was at the bottom of the fill plug hole threads. The fill plug had never been out. 2014 Scab with 25,000 miles.