It isn’t the strongest tranny box out in the woods…but it will do as long as you know what you are doing! So sit back and pay attention…
Do not try to down shift into 1st, unless the vehicle is basically at a stop. However, you could shift down to 2nd from 3rd. However, you should keep in mind the speeds recommended. You can see for the Intermediate gear (2nd) on the “Caution” plate that 41 MPH in high range (transfer case) is the highest recommended speed. Of course it also sez 60 MPH in high (3rd).
Looking at it another way based on the Willys MB/Ford GPW Speed Calculator if you were to get it into 2nd gear at 40.8 MPH you engine RPMs are calculated to be around 3700. That’s really pretty high as compared to say 41.4 MPH in 3rd with 2400 RPMs (much easier speed on your engine).
So slow your speeds down and then shift. Slowing down to just 30.9 MPH gets you into 2800 RPMs which is better. Drop it down to 25.4 MPH and you end up with 2300 RPMs (even better).
Basically you should neither over rev the engine for the speed you want to go at nor lug the engine (too few RPMs). That’s why we start off in 1st and work or way up to 3rd. While the jeep might be able to do it – it isn’t wise to lead off in 3rd from a dead stop.