Great thread. I've learned this information with the assistance of my dear friend [MENTION=56]Adm_rsx[/MENTION] over time. Here I go:

Many companies (Frana, etc) actually weld gears together to make them stronger, which is great over OEM but crap if you want to change your gears once and forget about it. PPG Gears are made from solid blocks of high-grade billet aluminum, so you're getting phenomenal quality with them over everyone else. Added to this, is their lifetime warranty. Now, there are 2 gear types:

Helical Cut


And Straight Cut


You see the difference?
Helical: ///////////
Straight: ||||||||||

Helical gears are what nearly ALL transmissions come with from the factory. Now, straight cut gears are far stronger than helical no matter how you put it. They allow full-face contact as they interlock.

The biggest weak point, aside from the gears themselves, are the synchros. They're used to make the gear 'catch up' to the engine speed, and allow for smoother shifting for daily driving. Have you ever felt grinding as you're shifting or have a gear pop out? That's your synchro's reminding you how much they hate you. The real issue is that we all technically need to wait a split second between shifting gears in a synchro-based transmission. Why? Because the synchros are making the gear speed 'catch up' to the engine speed (rpm). That takes a second. Also, having synchros means less room for gears, so they have to be thinner (narrower) and thus, weaker. Starting to see why we're having the problems we all end up having?

Here's what we all want: Dog Gears (dog box). These allow for solid full-throttle shifts regardless of engine or transmission speeds (whereas a synchro setup is trying to match the two speeds, thus the tons of synchro problems). Dog gears are all straight cut. You pick a gear, you go in. That's it. The difference is you have to pick a gear and go for it. No hesitation allowed. PPG has their own special 'dog engagement interlocking system' that allows for much better gear engagement and are much stronger. And with no synchros, the gears can be larger (wider) and much, much stronger! And the best part is that PPG dog box gears CAN be daily driven and taken on long distances! Some companies don't have any oil passages, which mean no heat dissipation and no long drives. But PPG has our backs, and makes amazing products. From gears to final drives to synchros and everything in-between.

I hope all this makes sense. If not, ask!