Gassers use four gears (TT,MT) but consider the characteristics of performance: Do you expect to break the tires loose with the gassers as much as an electric would? Generally.. I'd say no.
My Muggy's center diff heated up so much because under acceleration, the center diff would be forced into action (even with thick plumber's putty as my diff lube), spinning the planetary gears around and forcing them to chugg through all that slime. When my Muggy ran the gas motor, there wasn't enough low end torque to strain the center diff as much.
I assume the same applies to the larger scale gassers. I believe they all have a solid center diff. Excluding that from consideration, under heavy acceleration, the only "give" would be either through loss of traction, or the front or rear differentials.
I'm concerned about the stock diffs holding up to larger wheels and tires, as well as more power. It will be interesting to see what happens when adding an extra pair of planetary gears. Things could heat up enough to cause the plastic diff casing to distort. Converesely, I think shimming the stock diffs as they are could help to prevent any failure without introducing as much heat.
