need help with getting a dependable setup

[ncalenda]

Here is my problem, I run my e-maxx on the sand, and if I try to gear it for speed, it thermal's like crazy. My goal, is to get 40+ mph on the sand with no thermal.

Here is my setup:
9920 warrior esc / with BEC
9xl motor
pro-line arm, 3.3 carriers, towers, and shocks
2 speed tranny
rrr spur 70/22
5S Lipo
12 lb truck, with lipos in

When I run in 2nd, it thernals, 1st is fine.

I also want to go with the strobe, since I have heard it is a better clutch.

When I run it on the sand, with the resistance, 2nd is no good with these gears, and I have plenty of torque, too much to be honest.

The motor was find, it was the ESC that was too hot. Can I just get a better ESC to handle this, so that I can keep this gearing (and handle the 51 spur when I get the strobe)?

Would the Monster Pro quark-125b handle it better? Or, what esc can handle this, the motor seems to be fine.

Again, I do want to go 40+, on the sand, high resistance. Also, I want to get the single speed tranny, but can't if I can't even run it in 2nd now. If I can get it running how I like, then I will get the single tranny.