It is good practice to change them fairly often, so your diffs don't leak. I don't think this is your problem though. when you say your car only has 20% of its power is it because something is slipping or is something is binding up? I'm thinking that you haven't done up a grub screw in one of the drive shafts or something.

Also i agree that your diff oils are weird but they are nothing to do with your lack of drive.



I remember trying the 3-3-5 setup in my hyper 7 from the advice of a one of the hyper 7 gurus, he also had a full explanation of why it worked and that it was only a hyper 7 thing. And he was right it works really well i never liked the set up and went back to a more conventional setup but it was interesting to try.

Spider diffs also work slightly different to standards diffs as they are stiffer then a standard diff with the same oil in it at high differential speeds.