Well I am speaking from running high power setups, so I am using my personal experience. For a little bit I slapped in the 550 can 2000Kv and 80A esc from my Losi 8ight, just for S&G's one day, and ran it on 4s. I had to brake to turn, just because the front end wouldn't stay down! I also blew a couple tires off the beads. I run 15k weight Losi fluid in the front diff, 50k-100k depending on track conditions for the center, and 10k Losi fluid in the rear. My slipper just sits in the toolbox in case I royally screw up and toast my center diff. But with how well maintained my truck is, I doubt I will ever need it. Oh, and for track days, I run ROAR legal equipment as dictated. 2s Turnigy LiPo, CC MMP SCTE ESC (So many letters!) and a NeuCastle 3800Kv 4-Pole. A wheelie monster if it can keep the tires from losing traction. On 3s, it is the same just.....more. Actually TOO much for racing anyway, IMHO.

What I am saying is his issue is not from the 3s, or his power system. If his diffs are dry, or empty, then there will not be enough resistance for them to rotate efficiently. If this is not the issue, then new diffs are the answer. These drivetrains are much more simple than they seem, so there is not too much to troubleshoot.

1) Is the pinion and spur interacting properly?
2) Are the diffs themselves (all 3!) in good working condition?
3)Are the diffs filled with proper fluid of proper weight, and sealed properly as well?
4) Are the outputs all working and fastened as they should be?

That is about it. The drivetrain should be fine if everything is in order. If not, then you know what to fix!<br type="_moz" />