How often does the differential fluid need changing?

I also read there's a front and rear differential and they take different type of fluid.

How would I know if I have a limited flip differential?

I just purchased a 97 f150 v8 lariat with 158k miles. Could have more as the odometer wasn't working when I orchard it.

Id like to change the fluids out tomorrow if possible.

Thanks for your help in advance.

 

1. Every 100k.
2. Front takes 80w90 or 75w90, rear takes 85w140 synthetic.
3. Look at the AXLE code on the door jamb sticker, if it begins with a letter it's LS (ex. H9), if it begins with a number (ex. 19) it's non-LS. If it's LS, go to the Ford dealer and get a bottle of friction modifier to add to the fluid.

Factory uses RTV instead of a gasket, but you can use a gasket if you prefer. Autozone should have them.

VERY IMPORTANT - make sure you can get the fill plug loose BEFORE you pop the cover!

 

Thank you very much for the info. It was very helpful. The oil that drained out didn't look bad at all, but the fill plug had a gray sludge or grease type blob on it.

In watching a you tube video someone was saying gray sludge in the pumpkin means it's a sign the axle is going to grenade.

Any truth or insight to this?




Oil dripping out looks pretty clean



Sludge on inside of filler plug

 

Filler plug may be magnetic to attract any metal particles from normal wear. Not an issue.