This is for Standard Transmissions where you manually change the gears.
Most of us like to put one hand on the wheel, and the other on the gearshift while we drive, especially while in traffic. However, according to Silver Sport Transmissions (SST) resting on your shifter could be bad for your transmission.
As those gears spin, your shift forks are waiting to move the gears from one to the next and the synchronizers can come in contact with the gear and slowly wear on the teeth. The synchronizers don’t need to be engaged in order for them to come in contact, and resting your hand on the gearshift can cause the shift fork to apply pressure to the synchronizers. For this reason, Silver Sport Transmissions suggests that you do not rest your hand on the shifter, and only grab the shifter when you’re ready to shift.
“The fork pads were broken and the 5th gear’s teeth were rounded.”
"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."







From: Should You Rest Your Hand On The Shift Lever? Silver Sport Says "No" - Chevy Hardcore