I guess there are the two types, the Rear axle and the front style (I'm not sure how that is set up).

I am guessing the front type is the best? which brands have this transmission? Are the rear boxes durable, it seems there has been many problems with them and a old weaker gear in them. Do the front type have problems?

 

The rear reverse has a few problems. The biggest problem is its weight. It really affects the handling/suspension of the quad. I have had no mechanical problems with mine, but I drained out the stock gear oil. (2ozs) and put in 8ozs of 90wt gear oil. I have not seen the new reverse yet but moving it to the engine has to be a much better idea.

 

Mine is by the engine and it shifts flawlessly, and knock on wood, no issues after 7 months.

 

I have a JetMoto 150 with the reverse gearbox on the rear axle. I have not had any problems with it. It actually works pretty well. I did change the gear oil once I got it. I do think that if it is not adjusted properly and enough throttle is applied it will break. Mine gets ridden pretty hard and no issues with the gearbox so far.