hi, i recently changed my differential gear oil with the ungraded 75w-140 revision but was unsure if i needed friction modifier.a part store or 2 said it's required.so i added the 7 ozs instead of the 8 ozs because that was the only size bottle they had.later i found a video showing the different types of ways to tell what type of differentials there are and that whether i need the modifier or not.all that was said if if it's this or that type to add or not..but what wasn't specified is if my type that doesn't require it and do not add...so my question is if my diff doesn't require it once i determine what type i have, will putting it in hurt it or not make it work like it was designed to?thanks.

 

We would think if it was harmful to gears and bearings it would harm the differentials that require it

Since it only reacts with friction discs in differentials most likely would not harm a regular differential.

If you are still concerned, just open it up, drain the rear, assemble it and fill with lube.

 

The friction modifying additive won't hurt a thing and there is no reason to drain and replace your new gear oil.

 

Keep in mind the lube for the differential also lubricates the wheel bearings.

When filling allow time for the lube to flow into the wheel bearing housings and recheck after a period of time to make sure the level is at the correct point..