what does 1-2 and 3rd gear do?

on my AW4 I have always wondered exactly what 1-2 and 3rd do. I'm pretty sure that 1-2 just starts off in first gear and shifts to second at the appropriate time then stays there? and 3rd starts in first and shifts to second, then third. does it lock the torque converter in third?

1-2 is for off road, it holds the tranny in 1 or 2 for better torque and throttle control and in 2 for compression braking. 3 is for towing and for compression braking on mountain roads. I don't think 3 engages the lockup.

so i should use 1-2 for offroad? up to what kind of speeds can i use it? and use 3 for only towing or can i use it for city driving too?

If i'm in steep hills offroad, i'll use the 1-2. On my 89 it stays in first gear only, it has never shifted to 2nd gear...So as you can see i won't go over 5 miles per hour in 1-2..

The selector adjusts the ranges the transmission will shift though like the above posts.

1-2 starts in 1st, and will shift into 2nd when the pressure in the governor allows it to, generally towards the top of the RPM range.

3rd gear selection, allows for normal transmission operation and shift points up to 3rd gear, and will allow converter lockup at light loads.

1-2 anytime you need a low gear. Off-Roading is an example.
3 - Towing.
D - Normal driving.

You can use 3rd for city driving, it just won't shift into OD when you hit the highway unless you move the selector to D.

Third gear does engage the TC lockup. It happens, on my '92, somewhere around 38 MPH or so, and on my '96, a little north of 40. On both my two, and my son's two, the lockup in 4th, or Drive, happens at about 43 MPH. One thing you can do is when you're pulling a hill, with constant pressure on the gas, tap the brake pedal quickly with your left foot, and it will unlock the TC, and it will feel like passing gear. Another thing I will do is if you need to manually downshift from fourth to third and the TC is locked, tap the brake quickly, and shift to third. It will smooth the shift, as it is a one gear jump, instead of feeling like two.