how do i know which plug on the esc goes to the hole on the motr?

It doesn't matter.

How about the battery? I tried both ways, and there was a spark right where the battery, and esc plug in. Did the spark ruin anything?

No, a spark is usual although its possible if you tried the battery both ways....Only one way to find out although its unlikely.

I re-sodered (spelling) everything, and it seems to work now with no sparks.

Was it a big spark or what? If it was a big spark then it would have been shorted. But a small spark is usual...at least for my 9920 and others like it. Not sure about the MGM though.

It was a little spark. I turned everything on to see if it would work, and i cant figure out how to program the ESC. After 10 seconds it just keeps beeping, and a red light is flashing.

Also the motor jerks foward a tiny bit every time it beeps

Did you read the manuel?

Sparks are normal when plugging the batteries into the controller. This happens because the capacitors on the controller charge up very quickly when there is a potential difference provided to them. The spark is merely representative of a high inrush current.

yeah, it's because the internal resistance of the capacitors that are used on the controller are near 0 ohm when unused/uncharged. the 2nd time you plugged it in, it's likely that there still was some juice in them left, so that's the reason it didn't spark the 2nd time.

If you swapped the poles on the batteries, the spark woult be quite a bit bigger..

Well i order the rong pinions 2 times, and hey dont make the right pinion so i cant use the truck. If i want to make it work right, i have to buy a 8s with the standard size shaft, and buy new batteries. Im just going to returning everything, and selling the fu*king truck, unless the fiegao 12s has the 1/8 inch shaft.

what is the problem? i got my 8S with a 1/8th shaft and i just bought some HPI pinions (i thought the ones i bought are 48p)

No i have wanderer 12s with the 5mm shaft, and they dont make a pinion with 5mm bore, and 48p

I have seen the 48 pitch pinions in 5mm shaft size. If you want to know drop me an email or pm. I don't think mike has them but he may be able to get them. You could drop him an email to see.