2010 FX4 | 9.75ELD | MC 75w-140 | 13300 Miles

[CarbonSteel]

Here is the UOA of the first OC on the rear differential on my FX4. The oil was grey and I was concerned there was a fair amount of metal in it. There was quite a bit of iron in the oil and I think this UOA is good evidence that early changes in differential oil are very beneficial.

Thoughts and comments always welcome!


Here is the fluid:




Here is the UOA:

 

[panthermike]

Looks fine, did you put Motorcraft 75w140 back in?

 

[CarbonSteel]

Originally Posted By: panthermike
Looks fine, did you put Motorcraft 75w140 back in?

Yes, I did (it is synthetic) and the friction modifier. I had the dealer change all of them (front, xfer, trans, and rear) due to front axle has to have some suspension/steering components moved to gain access and all of it is under warranty.

 

[Steve S]

It is a good idea to change the break in fluid !! My wifes 2002 Superdutys diffs oil was grey when I changed it out when new.

 

[Rob_Roy]

Good call on getting the break in oil out.

At 80k my F350 had so much metal in the gear oil that it fouled the speed sensor with filings. I had to clean everything with solvent, and then do a short-run and another drain before putting in fresh 75w140.