It's all about friction!
You can put almost any kind of lubricant in between (with exception of shoe goo, CA cement, etc...
), so you can adjust your side movements (traction in corners).
Use a thick lubricant and the rearpod will move slow and has a lot of friction (the car will lean longer in the turns).
Use a softer/thinner lubricant and the rearpod will move more freely and with less friction (the rearpod will easier go to center when you're in a turn).
You can somewhat compare it with the oil in a shockabsorber, the same thing happens there.
In the end it's just another tuning point, just like so many (like; T-bar, shock, camber, caster, tires, etc...)!