Hey guys I have a 2000 f150 4.6L 4X4 5speed with 140000 miles on it. I dont think the differential oil has ever been changed, what oil have you found to be the most effective? Is lucas as good as everyone says it is?

 

Haha....Lucas is probably the worst thing you could put in your differential......ever!! And for 2 reasons..... 1: If your truck has a limited-slip, it will convert it into a lotta-slip. And 2: The stuff turns into a foam when it gets slung around at high speeds.....not what you want!!

Just use the recommended OEM fluid.......with friction modifier, if required. Also, if you do have a limited slip, now would be a good time to replace the clutch packs. And, spend the extra couple bucks....and get a gasket.

 

Thanks for the help. Would you recommend synthetic oil? I used full synthetic oil in my tranny and i love the way it shifts now.

 

The recommended is synthetic 75W140 (your manual states 75w90, but Ford changed it's recommendations a while back).
If you have limited slip, it will also require a bottle of friction modifier, assuming whatever you buy does not have it in already.

 

The factory fill is full synthetic, and full synthetic is required.

75W140 in the rear, and 75W90 in the front. Synthetic is not required in the front, but you might as well use it.

 

75W140 synthetic. I use wither Redline or Royal Purple. I don't add the friction modifier. It is not needed with these two brands.

Regards

Jean Marc Chartier

 

Thanks again guys this is really helpful.

 

Lucas Oil meets Ford's specs, as well as Red Line & Royal Purple. All three already have the friction modifier added so that you will not need to purchase it separately. I've used Lucas Oil in Ford trucks without any problem what-so-ever. Just check your maintenance schedule. I just picked up 4 quarts of Royal Purple from American Muscle for a very reasonable price.