changing the center diff oil will "Help" in the transfer of "power"
in other words going Higher in a CEN diff for example from say the Grease to 3000 diff oil
is about the "Equivilant" to about 8000 to 10,000 on a regular diff....but this will "Vary" as to how worn the internal gears are etc......
when the Matrix Buggies were "First Released" we tried using "Gear Oil" this helped a little...
60 and 90 wt gear oils seems to work well....so many tried doing the same for the trucks...
in a nut shell the higher "Viscosity" the center the more 4wd transfer....but will be little harder to steer...as well sometimes rough track handling may suffer.......
going to low in the center will cause the power to transfer to either too much to front or rear usually will be to the front....causing the tires to "Ballon".....making the car seem like it is too soft....
for the front and rear run 1k in front if there is no "Gear Oil" you can find..
(motorcycle shops will have this)
keep the grease in the rear...

if running "Standard diffs" or the cross pin conversion run 5k in front 7k in center 3k in rear the truck will be "Glued to the track" will handle real close to the New Thunder Tiger Pro's and Jammin trucks......
these are General guide lines....but track conditions will vary and may or may not apply directly to your track.....