Hey guys, I changed out my diffs to the Royal Purple 75-90 extreme gear w/ friction modifier. Do I need to add more friction modifier or should I leave it? Now it's snowed and I can't check it, although it bit and crawled up my driveway. Anyone have any suggestions? Thanks, Kurt

 

If you are not getting any chatter from the diff don't add more modifier.
If you add too much it will be like an open diff.

 

I didn't add any. I'm just wondering if the Royal Purple w/ modifier in it already is enough. I can't check it with the fig.8 trick because of snow and ice here. Thanks, kurt

 

It is impossible to know if there is enough FM in the gear lube until you can test the truck on pavement with some traction.....you want to add just enough to stop the chatter. If conditions are too slippery to adequately test, don't sweat it - lack of FM won't hurt anything until there is decent traction to cause some chatter.