The thing you are referring to needing is a viscous coupler unit or center differential viscous coupler. Some cars have just a coupler some have a coupler build into the center differential. Most cars are electronic control now. Only older Subarus with 5-speeds use this for the 50-50 split.
Does it only have when you turn it one way?
If you don't feel any binding, I'd say it's something else.
Mismatch tires and or tread could also cause this.
Always start with the easy stuff.
-Bad Wheel bearing
-Bad CV joint
Last edited by RumbleRumble; 07-06-2015 at 08:14 AM..