2019 KR 3.5 ecoboost. 6' bed. rear diff is wet on the bottom.....indicating a leak but I haven't pressure washed it yet and investigated it. Are rear diff leaks a common thing? I've been driving Ford Diesels since 1999....a 7.3, two 6.0's and a 2021 6.7...none have ever had rear diff leaks.

Also fluid capacity is appreciated and is a limited slip additive necessary?

Thanks.

 

Capacity is listed in the owners manual along with any additive information.

 

OF COURSE IT IS! Thanks! I don't know why......I NEVER open that damn book!

 

Capacity is fill until it leaks out. Additive only needed if you have limited slip. E locker does not need it.

Pinion seals are pretty common on these.

 

I know how they fill....just need to know how much to buy.

Pinion seal....good thing I bought an extended bumper to bumper through Ford.

 

The pinion seal on my pavement princess started leaking at around 50K miles.

 

I have 2018 and need to replace my pinion seal as well.
Just purchased truck, 5.0 4x4, with 124k miles.
Could hear the rearend wine when test drove but got it for a steal.
Had less than a quart of oil left in it, but actually looks good inside. Actually too good and clean, which leads me to believe someone was in there trying to seal the back cover and cleaned it.
After cleaning, resealing and filling with the Valvoline synthetic 75w/140 it is much quieter but can still hear a very slight whine @ slow speeds.
Hoping for the best of course, but now that I cleaned it up spotless and can very well see front seal is leaking, was wondering how feasible it would be to change bearing behind the pinion seal while I am there?

 

Open it and red it. You buy a vehicle used from a dealer you won't get one.

 

pinion seals are cheap and easy to replace.

 

Just the seal and torque the pinion nut.