I have searched on here and have got a mix of opinons so after some research this is what jeep has to say, so here is some much needed clarification on this foggy issue

What is the difference between Full-Time & Part-Time 4WD systems?
Full-time 4WD systems utilize a center differential, which enables the front and rear driveshafts to turn at different speeds, thereby allowing engagement on dry surfaces for normal driving conditions. A part-time system does not employ a center differential and locks the front and rear driveshafts together. With a part-time system, 2WD mode should be used during normal driving conditions and 4WD mode is to be used only when off-road or on wet or slippery surfaces.

Can I shift into 4WD High-Range at any speed?
Shifting into 4WD High-Range can be made with the vehicle stopped or in motion. If the vehicle is in motion, shifts can be made up to 55 mph (88 km/h)

How long can I drive in 4WD High-Range?
With a part-time system, prolonged driving in 4WD high-range is recommended only for wet, loose, or slippery road surfaces. With a full-time system, you need not worry about switching to 2WD mode when road surfaces improve.

How fast can I drive in 4WD High Range?
You should not go faster than road conditions permit.

Can I shift into 4WD Low-Range at any speed?
No. With the vehicle rolling at 2 to 3 mph (3 to 5 km/h), shift an automatic transmission to Neutral or depress the clutch pedal on a manual transmission. While the vehicle is coasting at to 3 mph (3 to 5 km/h), shift the transfer case lever firmly through Neutral and into the low-range position

Can I shift into 4WD Low-Range when stopped?
Shifting into or out of 4WD low-range is possible with the vehicle completely stopped, however, difficulty may occur due to the teeth of the gears not being properly aligned. The preferred method to engage the low-range is to slow down to 2 to 3 mph (3 to 5 km/h) and put the transmission in Neutral. While still moving forward, move the shift lever firmly into the four-low position. Then return the transmission to the desired gear.

How fast can I drive in 4WD Low-Range?
Do not exceed 25 mph (40 km/h).

 

into four high you can do it while driving under 30 mph failure to do so can result in damage from little to catastrophic. Into four low you should be stopped and have the transmission in neutral. Same procedure for shifting out.

 

 

I've shifted mine in and out of 4H as road conditions dictate at highway speed for years, never a problem. Owner's manual says 'any legal speed'. Where did the 30 MPH limit come from? Did you have one fail?

 

Where's cruiser when you need him lol. With the np231 to shift on the fly at ANY legal speed, and above, take foot off accelerator, firmly pull handle to 4h and keep driving. I've shifted on the fly at 65 mph and didn't blow up. NOW, obviously you shouldn't shift the np231 into 4wd on dry surfaces or there can be issues. As for 4lo. I've heard no more than 10 mph but I only use it offroading so I can't answer that for sure for ya. Ie seen people who have regeared drive easily in 4 lo with no issues all day

 

Thanks for the information from the owner's manual. Guys - look at the first post. This is how the transfer case is supposed to be operated.

It's nearly impossible to screw up a 4H shift, the mode hub has plenty of teeth. 4L however has a small unsynchronized gear that you need to be careful eith, and does require a little spin to get to mesh.

I am curious as to who made up all this stopped/10MPH/30MPH nonsense and why.

 

yes my owner's manual states what the OP posted as well. I have made 4H shifts going 50+ numerous times without ill effect.

4L - well I've only used it to pull some stuff a couple times, but it does work. I was stopped when I engaged it. worked fine.

 

radi : two. I have lost two transfer cases on different jeeps by shifting into 4 wheel while going faster than 30 mph.

salad : chrysler engineers. Yes it's an engineer and we know how accurate they are.

 

The first post in this thread is from Chrysler engineers.

 

I have no problem shifting to 4Hi.

When I shift out of 4Lo, I have to go all the way to 2 wheel and then back to 4hi if I want 4hi. Otherwise I grind.

 

If you lost 2 t-cases from shifting in to 4hi over 30 mph im sure that they were already were on the way out... im not always going to shift in to 4hi at freeway speeds and if I ever had to I would most definitely slow down before I did. This information can also be found on the jeep website.

 

Make sure when shifting on the fly, you are never in the accelerator. Always release shift firmly reapply. As for 4lo. Go to a crawl, shift tranny to neutral, shift to 4lo, may need persuasion I not done often and thn shift to gear when its in 4lo. Easy a blue trails. Or shifted numerous times doing 60 when the weather sucks out and haven't had grinding, binding, screaming, yelling, kicking, cursing, sweating or melting.

 

How accurate are we?

 

Ive had mine in 4 hi and doing 80mph down the highway in a snow storm. And in 4 low ive ran up to 40mph and never had any issues

 

Really?

Here's what the manual says:



Here's how the factory suggests you shift the transfer case and I've been doing this since these things were new and I worked at the dealership. Quoted from the owner's manual.

"To engage, shift the transfer case lever from 2H to 4H while the vehicle is moving at any legal speed". I let off the gas, throw the lever, and then tap the gas and let off.

4L position: " To engage, slow the vehicle to 2-3 MPH , shift the transmission to Neutral, then shift the transfer lever to the right and pull firmly rearward to 4L".