i may work on a 4 gear transmission not that i have access to autoCAD and a friend with a CNC. make it out of delrin or something, using the losi gears.

Have you seen the Atomic Carbon Losi trans mod to convert the motor to RH mount???? its a slick little kit but since it comes from the u.k. i was curious of cost...
I am going to go with the external 4th gear on my truck with a new motor plate and an adj 4th gear to accomodate large and small spur gears along with the motor adjustment.

are associated rear b44 arms very tough? because i will probably have to use them in the back. or maybe RB5 rear arms would fit?

I thought B44 and B4 used the same rear arms.

Yep. I think they do. Now I need to know if they are durable

Well i have 2 B4's and have never broken a rear arm myself..

On the B4 it's usually the front c-hub if anything,on the t4 it was c-hubs and front arms, the rears on both are stout though, same with the rear hubcarriers-stout.

are a123 batteries legal for most 2wd buggy classes?

As far as big races go, I don't think so. I dont think they are ROAR approved. But local? Sure. You'll have to run Mod because the voltages don't match Lipo or Nimh so you will be down on power in a stock class.

^what he said :)

does 6.6v make that much of a difference in speed from 7.2v? the a123's are 30c and a 6.6v 2300mah a123 is way lighter then most lipos. so i would think that the speed wouldnt be that much slower?

i used a 6.6 li-fe in a stock blitz and it was quite slower...not too significantly but noticeable. it would be better suited for mod. where you can still be pretty fast. in 17.5 you need all the voltage you can get to competitive.

also you guys looking to use the a-123's remember that our li-pos peak out at 8.4 volts, and generally STAY above 8v running stock. So running a 6.6v pack that peaks out around 7.2v you would still be at an almost 1.2v deficiency compared to those running li-pos. In a stock class where 1 tooth on the pinion can make a HUGE difference, I dont think the a-123's would hold their own.

For a given load (stock motor) power is relative to the square of voltage. So just using nominal voltages for the moment, the ~12% voltage difference (7.4/6.6) is nearly 26% in power. Fairly substantial.

I believe if you look at voltage under load throughout the discharge curve it will be an even bigger difference.

Well I guess I will have to go with nimh's or some cheap 1s lipos wired in series from hobbyking