I got the Ultimate Edition II gearbox now, here is my little review:
* They are well made, with clean steel gear and all bearing, chromed metal plate, etc;
* They are smoother than pot-metal ones, after I dis-engaged the motor, I can feel the gear box is really spinning well.
They worth the price, even you have to buy it off TAOBAO - the Chinese version of ebay, and shipped it over from a third party dealer - TAOBAO seller don't speak English, and never ship over sea.
They improved linearity a lot but not to the degree of realistic smooth -- I am very picky here, it is actually acceptable job for sure.
A further thought is the tank itself, Henglong hull and wheel can be bent, untrue, wobble, tweaked easily with some force on them, misalignment adds friction.
Gear box is also a problem, i my opinion, there are too many level of gears, and the small gear won't have the required accuracy. It is better off to use 540 motor to begin with, and using only worm gear for maybe a couple of level of reduction. I will certainly try Tamiya style gearbox in my next project,
The last edit is: If you can't get the ultimate version, you can get a steel version. A chinese forum post an innovative mod, using drill chuck to hold the gear axial, take it as a lathe, and grind it down from 3.5mm to 3mm contact, then replace brass bearing with the flaged ball bearing. It is not too hard to grind off only 0.25mm radial.
Last edited by modeleryang; 02-03-2015 at 07:58 PM.