The Selec-Trac® transfer case provides 5 mode positions –
1. normal 2-wheel drive mode
2. part-time 4-wheel drive high range
3. full-time 4-wheel drive high range
4. neutral
5. 4-wheel drive low range.

This transfer case is equipped with an inter-axle differential which allows driving the vehicle in the 4 FULL TIME position at all times on any given road surface including dry hard surfaced roads. The 4 FULL TIME mode allows the front and rear wheels to rotate at different speeds which eliminates driveline binding and component wear that is normally associated with driving the vehicle in the 4 PART TIME position on dry hard surfaced roads. This feature provides the safety, security, and convenience of operating in 4–wheel drive at all times regardless of road conditions.

When additional traction is required the 4 PART TIME and 4LO positions can be used to lock the front and rear driveshafts together through the transfer case inter-axle differential and force the front and rear driveshafts to rotate at the same speed. This is accomplished by simply moving the shift lever to these positions.
The 4 PART TIME and 4LO positions are intended for loose, slippery road surfaces only. Driving in the 4 PART TIME and 4LO positions on dry hard surfaced roads may cause increased tire wear and damage to driveline components.

So it’s for dry hard pavement? I think I’ll keep using 2wd for that lol. As I thought, it’s a useless mode.

I have the same T case in my hmmwv, except they omit the 2wd position. So for that vehicle it is for dry pavement, only because they don’t provide 2wd.

It's not useless. The main advantage of 4FT is that you're not going to risk steering bind while turning because the centre differential allows the front and rear axles to turn at different speeds when unlocked. Effectively, it's an AWD setting.

Advantages: being able to maintain a reasonable speed on hard surfaces in adverse weather conditions with significantly better control of the vehicle; making sharp turns (or turning around) on trails where 4WD is needed.



That's the 242AMG, which also gains a extra chain and external oil cooler over the 242J in the KJ / XJ / ZJ / WJ and a couple of others I'm forgetting. If memory serves, it is possible to engage 2WD with the Hummer case, but shifter linkage (and possibly other) modifications are needed to allow access to it. 2WD isn't 'removed' as such; it's just not accessible in stock form.

Also IIRC (and it's been over a decade since I was last in an HMMWV), that transfer case should have a shift pattern that goes HL-H-N-L. HL is equivalent to 4PT, H is equivalent to 4FT (and is the range that should be used on hard surfaces, including roads), N is also neutral, and L is the same as 4LO. It has the same centre differential as the 242J does, so capabilities are the same.

Think of full-time 4wd like all-wheel-drive.
You know, like a Subaru

I use it during heavy rain.
Great traction and handling on wet and flooded roads.

And to add to the above, if you're on icy roads going at a relatively high speed, part time will make you break loose, where as full time will be less likely to do so. Now, if you're going really slow on those same conditions, or roads so slick that you're limited to a max of 25mph or so, then part time is more helpful. But, dont use it if you're going to hit bare pavement or full traction.
I rarely have a road so slick that I use part time on the pavement, only solid ice going very slow...

Offroad, I use part time primarily if I need more traction. Then the lockers when it gets serious.

4WD does not increase your traction. It MIGHT increase the torque applied to the road, but if you are towing that heavy that 2WD isn't sufficient... You are likely WAY over what the engine should be pulling.

4WD does not increase your traction. It MIGHT increase the torque applied to the road, but if you are towing that heavy that 2WD isn't sufficient... You are likely WAY over what the engine should be pulling.

Having had multiple Jeeps with both the NP231 and NP242 transfer cases, I'll take an NP242 over an NP231 any day. 4FT is a large part of the reason for this - when it's needed, it's invaluable. It may not be obvious what the value is, but I can say from experience owning a variety of 4WD and AWD vehicles, it's made me a fan of lockable centre diffs.

4WD does not increase your traction. It MIGHT increase the torque applied to the road, but if you are towing that heavy that 2WD isn't sufficient... You are likely WAY over what the engine should be pulling.

I do a lot of fast pace winding gravel roads and 4FT is the ticket ! For any season.