Noisey 4x4 np231??

So it was pouring really hard over here in SoCal. Just the other day I was going up the canyon road and my 98 XJ AW4 Sport and the rear end started slipping. So I decided to put the thing on 4HI and shifted the transfer case into 4HI. The shift was fairly smooth but it started making weird noises. I don't know if that's normal when its on 4HI but I kinda got freaked out decided to shift back to 2WD. The "part-time" light came on btw.

How fast can I go while im in 4HI? How do I shift into 4LO? Just shove it right down? I read the owner's manual but it wasn't very clear as to 4x4 operations. Let me know

x2 I think Jeep recommends not going any faster than 45 MPH in 4HI, 20 in 4LO. And I tend to only use it when its snowing to the point where its white on the road.

You should also be only rolling when shifting into 4 lo.

oh okay so if i want to shift to 4 LO I pop it in neutral let it roll then shift down?

Nuetral or clutch in.. for 4 low.
I would say 40mph max for 4hi

What kind of "wierd" noises when your in 4wd?

blackhawk411 said:

oh okay so if i want to shift to 4 LO I pop it in neutral let it roll then shift down?

Click to expand...

Hopefully this helps, I don't mean to give you the long-winded version, but I figure more is better than too little.

yes however, when I shift into 4Lo, the road conditions are to the point where I'm trying to crawl out of something--i.e. snowed in at a parking lot (or towing someone out of said parking lot), crawling around on a hill--its only for situations where you need a lot of torque. When shifting into 4Lo I generally try to stop the jeep if I can and then throw the shifter--the ratio difference is pretty big--at least slow down to 10MPH.

Noises: If the noises in question go away a few seconds after shifting into 4WD, its most likely because you're moving and its merely the 4x4 (more specifically the front drive shaft) engaging. If the noises cont. then you might have a problem.

Part-time vs full-time: You Jeep has both part-time and full time 4x4. Meaning that in 4Hi it will be in part-time; you basically can drive the car like normal (steering-wise), as well as on just wet roads if you want to. It allows the wheels to turn at different ratios--the wheel on the outside of a turn needs to spin faster than the inside wheel--but still provides power (in different amounts however) to both wheels. 4Lo should be full-time 4 wheel drive on your Jeep, meaning that the wheels are 'locked' (term used loosely) and will be provided the same amount of power, and must turn at the same ratio--therefore when in 4Lo, you shouldn't be driving on anything less than a slippery surface, and should not turn sharply.

I'm not an expert by any means, but hopefully that helps you out. Others--feel free to correct me, I do drive an 84, but I think that all of the above applies to your year.
Ed

ive been in 4 hi at well over 40mph.

where are you guys getting this info about 4hi and 40mph as the max? where is it written or are you just assuming/guessing?

ok, well start with 4hi. you can enguage 4hi traveling at any speed 55mph or under, after its in 4, you technically can go faster but i dont see why or when it would be safe to do so. you will hear a SLIGHT whining noise when in 4hi, thats just the 4wd working. and also, be sure to never put it in 4 when the back wheels are actually slipping, or you will grind you tcase. a note about part time 4wd, the part time light on your dash will always come in in 4wd. part time 4wd is just that, meand to be used part of the time. NEVER use part time 4wd on dry or even just wet pavement as it will cause driveline windup or wheel hop and could break parts. unless you have the NP242, with the full time option you can't use your 4wd on dry or wet pavement, full time is that, its not so much a 4wd, it functions more as a AWD and can be used in any road surface, because it activates the center viscous coupling and allows the driveshafts to spin at different speeds. now for 4lo, as you already know, the tranny has to be shifted into N and you can only be rolling at a MAXIMUM of 3mph. i usually do it when stopped, just to be safe. the worst that will happen when enguageing 4lo when stopped is it will not go in, and you will have to roll forward to get the gears to line up. also, if you havent figured it out already, you have to go into 4hi, then push it to the right and pull it straight back. sorry for the long responce, but i just wanted to make it as clear as possible, let me kno if there was nething u didnt understand.

They werent saying that 40mph was the top speed for 4hi. he said it was the fastest he recommends to engage 4hi. I agree and as for 4lo I always try to stop and drop it into neutral before engaging it.

Alright this is just too much misinformation at once...

4HI - PART TIME - Shift into this while OFF the gas under the recommended speed limit of 40 mph. This LOCKS the front and rear AXLES together. Meaning that if you are on dry pavement or even wet pavement, you will bind something as you are trying to make at least two of your tires turn at the same rate.

4LO - PART TIME - Shift into this while in PARK or NEUTRAL rolling no more than 5-10 mph. This reduces your gear ratio a further 2.72:1 and LOCKS the front and rear AXLES together. This is really only needed for off-roading, SERIOUSLY slippery conditions, or when more torque is required (snow banks, mud, hill climbing, recovery).

4HI - FULL TIME (NP242 ONLY) - Shift into this while OFF the gas under the recommended speed limit of 40 mph. This DOES NOT LOCK the front and rear axles together. You can use this whenever you want (even dry pavement) as it is more of an AWD function than a 4WD function. The NP242 does not use a viscous coupling like the Grand Cherokees do, instead it uses an extra planetary gear setup. This is great for rain, flurrys, dirt roads, etc.

In reality I have heard of shifting into and out of 4HI part and full time at speeds up to 70-80 mph, but I would never try it. Why would you need it if you're going that fast anyways?

firefight343 said:

Part-time vs full-time: You Jeep has both part-time and full time 4x4. Meaning that in 4Hi it will be in part-time; you basically can drive the car like normal (steering-wise), as well as on just wet roads if you want to.Ed

Click to expand...

Careful here - part-time does not mean drive it around as usual - that would be full-time.

jeeptx23 said:

They werent saying that 40mph was the top speed for 4hi. he said it was the fastest he recommends to engage 4hi. I agree and as for 4lo I always try to stop and drop it into neutral before engaging it.

Click to expand...

no, this was said:

firefight343 x2 I think Jeep recommends not going any faster than 45 MPH in 4HI, 20 in 4LO. And I tend to only use it when its snowing to the point where its white on the road.


ive also put it into 4hi going 55 mph a few times without a problem.

just wondering where this 40mph number is coming from, why is it recommended. i would like to know where it is written.

The manual that came with my XJ says you can shift into 4hi at any legal speed.

The 40 mph number I have is coming from the manual of my 85 Dodge Ram.

NP208 Aluminum case, chain driven. Just a bigger version of an NP231 with a different low ratio.

It RECOMMENDED shifting into 4WD UNDER 40 mph (as far as I can remember...might have been 45 mph but it's irrelevent).

If you are going highway speeds and need 4WD, I would love to know what you're doing.

MoparManiac said:

The 40 mph number I have is coming from the manual of my 85 Dodge Ram.

NP208 Aluminum case, chain driven. Just a bigger version of an NP231 with a different low ratio.

It RECOMMENDED shifting into 4WD UNDER 40 mph (as far as I can remember...might have been 45 mph but it's irrelevent).

If you are going highway speeds and need 4WD, I would love to know what you're doing.

Click to expand...

doesnt matter what im doing, but i have done it. it was safer to go into 4wd than slowing down because of the change in weather condition and tractortrailers surrounding me.

dodge ram is a different animal. we are talking about the drive train of a jeep xj arent we?

Yes it is a different vehicle, but not an entirely different drivetrain setup.

Vacuum Disconnect front D44 (shift on the fly, same as early D30s).
Aluminum cased chain driven NP208 (Same setup as NP231, with only a different low range)

I should have restated. I have never felt a need to put it in 4WD on the highway. If there was a sudden downfall of snow and I was cruising along and didn't have time to brake...sure I guess it would kind of make sense.

Cheers to who ever suggested the misinformation.
I gladly admit I got confused there on the part-time/full-time, MoparManiac (in my opinion) is absolutely right. I get the 40-45 mph limit for engaging (my apologies 89xj)the 4hi from a Jeep article I read somewhere...is it set in stone, absolutely not. I figure it this way, by shifting in 4WD (in my 84 vac. disconnect) I am going to be making the front drive shaft engage and the gears in the diff. will have to line up, the slower I'm going; the less shearing effect might take place if the gears aren't lined up. I understand that in the 98 its a non-disco system, and its quite a bit younger than mine.

Hoefully I haven't made this thread go completely FUBAR, but in response to XBobJ's orig. question:
"How fast can I go while im in 4HI? How do I shift into 4LO? Just shove it right down? I read the owner's manual but it wasn't very clear as to 4x4 operations. Let me know"

-You can go as fast as you feel comfortable in 4hi (but if you're in 4hi, road conditions are probably not good enough to speed)
-Shifting in 4Lo stop (recommended) or go really slow; in Neutral or Clutch in

MoparManiac said:

Yes it is a different vehicle, but not an entirely different drivetrain setup.

Vacuum Disconnect front D44 (shift on the fly, same as early D30s).
Aluminum cased chain driven NP208 (Same setup as NP231, with only a different low range)

I should have restated. I have never felt a need to put it in 4WD on the highway. If there was a sudden downfall of snow and I was cruising along and didn't have time to brake...sure I guess it would kind of make sense.

Click to expand...

x2 if u need 4wd on the road i wouldnt be going 45, bad conditions= take it slow, waaaaayyy easier to lose control going faster