Jonathan Lim

On some (if not all) stampedes, one of the gears has two parts. These parts can easily strip, so it is recommended that you glue them together.

Here is a blog post explaining that.
And another
Other than that, there's not much that you can do to reinforce gears. There are several people that have been talking about making/selling replacements, though.

If you want to be a bit "safer" with your gears, maybe you should try this 6kg spring.

Thank you for the links

If you are only adding a 9kg spring to your stampede, there shouldn't much of a problem. My stampede is running an almost 9kg spring and it is holding up just fine so a 9kg is probably safe.

Did you do anything with the gears? At this point if my Stampede gears get stripped I'm gonna roll on the floor and cry

Actually I was going to upgrade to a Lipo build soon. Although the initial investment cost is expensive.
Currently what I've planned is I'm gonna run it on a 2s build.
7.4 volts shouldn't be too terribly bad since the 20C discharge should make up for voltage.
On Power Dash motors it should work fine.

Using trustfires with overvolted Tamiya motors is asking for catastrophic failure. People have reported trustfires exploding in things like flashlights. What happened in your case was the motors couldn't supply the amount of current that motor wanted at that voltage, that's why the batteries fried before the motors. If you tried the same motors with a 4S Lipo, I doubt those Tamiyas would last more than a few seconds.

I've seen modders like Drac who used Power Dash Motors on 3 Ultrafires. So, I'm unsure.

Thanks, but my story was the motors didn't get "cooked" . The batteries were the ones who got cooked LOL. Anyways, the motors
were performing fine for a few days then the batteries just died.