Hi! First off, thank you for being Ford lovers and for using your time to help other Ford owners!

My question is on my rear differential. After draining, I added 3.5-3.75 quarts and purchased another expecting to put in at least 1/2 quart more. It was a couple days later, but it was pretty much immediately full. Apart from “I had added the perfect amount the first day,” are there other explanations for what happened?

 

How did you go about draining the rear?

 

Opened drain plug to equalize pressure. Broke bolts on rear panel. Left one on top screwed in and removed rest. Used metal putty knife to break gasket. Drained differential. Removed panel. Cleaned out pool of fluid on bottom. Cleaned up old gasket while trying to keep inside clean. Cleaned rear cover with brake cleaner. Old gasket paste was red. Used new black gasket paste and then lined up and bolted cover. Torqued each bolt to 30ft lbs and then tightened to 35ft lbs afterwards. Put in drain plug.

 

Something to keep in mind.,
A rear axle assy when completely empty will not contain any lube in the rear axle bearing wells and that could explain why it did not require the full amount you expected.

When wheels are removed and rear bearing wells are drained, the proper way to fill them BEFORE moving the vehicle is to tip the axle in both directions to allow the lube to get into those wells.then recheck if more lube is required to bring the lube level to the correct level. I believe this should answer your concern, if not let us know, thanks.

 

Technically, I didn’t have an expected level of differential fluid. I was initially surprised that it took more than 3 quarts. When I put in the 4th and it all went in, I realized that it could still be user error, not getting everything in that I could have.

However, I purchased the 5th quart with full expectation that at least some would go in. But if any did, it was very little as it was overflowing almost immediately.

Because there was a few days idle time in-between the 4th and 5th quart, I was wondering if what I saw could have been explained by temp or another change. The first quarts seemed rather thick and solid, but it seemed liquid by the last quart. The oil “melting” might explain what happened too, if that’s possible. I had already “filled it up”, but it wasn’t leaking out because it was in a more solid state…