Here's a little tid bit I received from Silver Sport Transmissions.
A customer recently called us with a problem. His transmission was slipping in 5th gear and the problem was only getting worse. He had put some miles on it, but it would be considered a low amount of milage for a transmission.
When our builder opened the transmission up, it looked brand new! He soon found the culprit, however. The fork pads were broken and the 5th gear's teeth were rounded. We've seen this problem before and we knew what it was immediately. This kind of wear happens when the driver rests his hand on the shifter while driving.
Brass fork pads are sturdier than the plastic ones that come with the factory TKO, but brass fork pads won't prevent wear to the gear teeth. It's best to not rest your hand on the shifter at all.
Fork pads wear then break from constant friction when you rest your hand on the shifter knob.
Plastic fork pads will eventually wear and break with regular use, but you can upgrade to bronze fork pads and extend the life of your transmission's fork pads exponentially.
5th gear, which had started to slip, shows signs of wear and damage to the teeth.