"3" and "12" on shifting console.
 

I have a automatic 99 Xj, On the shifting console, there are 2 modes that I dont know what they do. What are the 3 mode and 12 mode used for? Thanks.

3 keeps it from going into 4th gear. In 3 the torque converter will still lock.

In 1-2, you can use gears 1 and 2. The shift from 1st gear to 2nd gear is at 4000rpms.

How does shifting into them work in a mechanical sense, if you know?
Can I shift into either while driving, and does moving over R cause any unwanted.. Reverse "action"?
If you can shift between then, do you still need to apply the brake to shift?

https://cimg9.ibsrv.net/gimg/www.che...e734fa7ad8.jpg

No you don't have to apply the brake to shift between D, 3 and 1-2. If you are shifting over R you are going into park, which you shouldn't do while driving.

Thank you, I was simply wondering what kind of procedure would be needed to shift into these when driving, and if there are any dont's about doing it.
I already knew the R and Park thing, I'd like to keep my transmission xD

Shifting into 3 while driving isn't a big deal, its basically the same thing as kickdown when you heavy accelerate except you are controlling when it down shifts instead of throttle position and rpms. When I ran trails in my old jeep I would run in the 1-2 range. Helps keep the rpms up while keeping a lower gear. I wouldn't recommend dropping into 1-2 st higher speeds.

I never knew driving an auto. might be so difficult ;)