Chaning Differental oil ???

[ilvtravln]

Have an 03 F350, 90K miles, how often should the diff. oil be changed ? Ford lists the oil that came with is as synthetic. We do about 1/3 towing and the rest around town. Thanks

[dodge_guy]

When I had my TT I changed the diff fluid every 25k miles. It was easy for me to do and sometimes I had access to the fluid. I also did my trans fluid as often. Same for brake fluid.

[RAS43]

Yes, do it now along with transfer case and front diff. I have an '06 and change mine about every 5 years. But I live at the foot of the Rockies and tow a bunch in them. Towing is hard on gear boxes.

[BarabooBob]

On my F150, the transfer case was super simple. Pull the drain plug, let it drain, and refill. The rear differential requires removing the rear half to drain, reinstall and refill. For the front differential, I used a pump and removed as much of the fluid as possible and refilled it. Total job took me about 2 hours.

[agesilaus]

I did it on our 2012 F350 4WD including the transfer case and it was easier than I expected. I used the OEM Ford fluid. I also got a pump to pump the old stuff out and the new stuff in. Or did I use a drain plug? It's been awhile, definitively used a pump to add it back tho.

[wildtoad]

MitchF150 wrote:
20 year old gear oil... I'd change it.

This…..

[KD4UPL]

Read the manual for sure. It's probably either 50,000 miles or 100,000 miles depending on use. Towing and running around town are both hard on it. Long highway trips not towing would be easy life on the oil.
I'd change it.

[MitchF150]

20 year old gear oil... I'd change it.

[Grit_dog]

How often? Now. If it’s 20 year old oil. That said once I do an early diff change on a new or new to me vehicle, I go at least 50k between changes with good synthetic gear lube.

PS, if it’s an early 03 7.3 you have a very desirable vehicle if it’s been kept up and basically used only rarely.