kidkodiak

I've read a bunch of posts after searching this question... and Im still not 100% sure I understand the answer to my question.

I have 2 cherokee's... a 1990 that has a fulltime and a part time 4WD option, and I Have a 2001 that has only a 4WD option (one size fits all).

I'm used to driving in the winter snow with full-time 4WD. It works great, and when I hit spots of no snow, it still works great. The new Jeep though...

Here in WA, during the winter, the roads can be frequently a mix of compact snow and dry pavement (thanks to the rain), so it's variable slippage. I don't normally need 4wheel drive for these conditions.... but I did get used to being able to put it in 4HI and leave it there in bad weather. Apparently that's not an option for me anymore?

Here's my question, I guess...

If you had the jeep in "part time", which is my only option, and you had road conditions that were slick, dry, slick, dry as you drove, are you gonna break something if you keep it in part time? how bad is that for the Tcase? How likely to break something? I haven't tried using 4whl at all on it yet in snow... I tested it on wet pavement after a hard rain and it jerked and bucked around and made me nervous that I was going to break a driveline or something.

I read this quote (below) from another post, and this makes it sound, to me, like I cannot engage 4WD until I'm actually slipping... no preventative option allowed. If you slip, engage it... if you're not slipping, keep it in 2HI. If you're slipping, hope you can engage it in time so as not to crash during said slip... =\

Is that correct?

Here's the quote:
From a post here: https://www.cherokeeforum.com/f2/when-shift-into-4wd-7235/

Can someone help me understand this system? Is this transmission worth it? I kind of liked having the Fulltime & PartTime option in my 1990.

I guess I can keep driving that in bad weather, but it's getting on in years and miles and will pry need to be retired soon.

mike37

its not a good idea to drive in part time on the pavement to much chance of binding

BudgetXJ

What JeepCoMJ said in that quote is bang on. Do not run your jeep on dry pavement in part time. It causes binding which can cause damage to your t-case.

mike37

Originally Posted by JeepCoMJ
the main difference between the np242 and np231 is that the np242 has it's own "differential" that allows the transfercase not to bind between front and rear axles.

the np231, however, locks the axles to each other. so, there is no slip between the two, and it can bind up and detonate at road speeds on dry/decent traction conditions. the reason it would detonate is because the front axle also gives you the ability to turn...when you turn, this creates a different travelling speed of the front differential vs. the rear differential, which causes the front input on the transfercase to attempt to move either slower, or faster. this, of course, isn't going to work since the 231 literally locks the front and rear shafts together.
another reason it could bind is the minor difference in rear vs. front gears...i.e. my rear dana 44 has 4.09 gears, the front has 4.11 gears. they're close, and what is available. however, "close" is only good enough in situations with at least a small amount of slip to allow for differentiation to accomodate the minimal difference in differential rotational speeds.

the np242 in full time acts as an open carrier would...it's not locked front to rear. the ONLY downside to this is more moving parts. more moving parts is almost always a quicker way to failure.

that said, there's nothing wrong with your np242. just don't drive it in 4wd on the highway...a friend of mine did that, and ended up with a driveshaft coming through the floor just missing his leg.


I think this is a type O its the 321 you don't want to drive pavement

kidkodiak

ok, so for in-town winter (eg: snow) driving... it's safer not to engage the 4WD unless you're actually slipping, do I read that right?

And is this transmission safe to engage while actually moving, or does this one prefer to be engaged when stopped + in neutral?

Thanks for the responses so far guys.

BudgetXJ

you can switch from 2hi to 4hi while moving. You still have to slip the tranny into neutral but you don't have to come to a stop. To go to 4lo, you have to come to a complete stop.

kidkodiak

ok, that helps me then. Thanks much

BuckB91XJ

KidKodiak, Where in NW Washington do you call home? You must be close to me.

kidkodiak

Bellingham. Yeah, not too far away if you're in Oak Harbor. How you likin' the rain the last few days?

BuckB91XJ

B-town is great. I'm not liking the rain. 4wheeling is great rain or no rain but, I am ready for some spring and summer wheeling.

kidkodiak

Yeah, I'm waiting (biting at the bit, really) for summertime fishing in the mountains. Gimme a warm sunny day, a fly rod, and put me 20miles from people and I'm happy

#999

so after many a page looking for a straight answer on here im only slightly confused now.
i know when and how to use both 4x4 settings on my 2000 Jeep Cherokee, but am not sure whats up with this 2 wheel drive high.......when is it safe to use that ?whenever i need a little grip...or dont use at all??
thanks

kidkodiak

2-wh drive high... that's the default position that you drive your vehicle in. It's not a special gearing

CherokeeSport98

My only problem with full time 4WD is that you cant replace one tire if you have a problem, you must change them all