If you have only 4hi and 4lo, you don't have a selec-trac dude. You have the command-trac.

I'm pretty sure you always have to manually put it in either full time or part time. I think that on the newer grand cherokees it decides when to change it, but don't quote me on that. Whatever setting its on, thats what 4x4 its in. I personally like the selec-trac. I have 2wd, full time, part time, neutral, and 4LO in that order. More options= more wheeling

The difference between part time and full time:
Part time: the front drive shaft is engaged constantly.
Full time: the front DS is only engaged when theres wheel slip.
Also, with these type TC's they are manually dis/engaged so it switching itself isn't an option.
Hope this helps...

Not true. The 231's are stronger than 242's. The advantage with the 242 is the full time feature. So roads that are half snow half dry this is a nice option...

How are they stronger? they have the same first number. That number is the size and also the strength of the transfer case.

Im pretty sure uve got full and part time backwards

Incorrect. The difference between part-time and full-time is this:

In FT, the power to both front and rear driveshafts from the transfer case goes through a differential INSIDE the transfer case which allows the front and rear driveshafts not to fight each other while turning on any hard surfaces. Hence, you can use it Full Time if you want to like going from black pavement to snow/ice etc.

In PT, both front and rear driveshafts are driven at the same speed and there will be driveline bind except on slippery surfaces where the tires can "slip". Hence, only to be used Part Time like on slick surfaces.

Now, if you have your transfer case in FT and go do some challenging off-roading and leave it in FT, all the power can go to just one axle. For instance, if you get a front wheel off the ground, all the power will go to that wheel. That's where PT comes in. Select PT for that situation and the transfer case will give a torque split of 50/50 to both drive axles.

So always use part time pretty much

No. FT for street driving where traction conditions are constantly changing. Or even driving dirt roads leisurely.

Where there's a chance you're gonna get a wheel airborne, use PT.

Ok thx

PT along with the D30 and D35 means lockers are pointless for normal wheeling. All 4 tires spin at the same time on my jeep. My buddy's tacoma only spins 1 front and 1 rear. I love my jeep

Atleast ive been doing it right for the most part I just keep it in full time ive never put it in part time but I never get the wheel off the ground

The owners manual for my 90 XJ says you can shift into 4hi at any legal speed on slippery surfaces. Ive used my on rainy days going 60 mph with no problems.

You are sorely mistaken. The only variable might be that you have a Trac-Loc in your rear diff.

You are correct. You can shift from any high range mode 2wd to 4wd and back again at any legal speed. I've done it over 80 before.