NP 231 usage.

Here in Colorado we have frequent, but short lived snowstorms in the winter. By short lived I mean that we get a snow fall event one day, and the next day its sunny and 50 degrees out. Those of you in Colorado know what I'm talking about.

The "next day" is a very difficult situation to decide how to use four wheel drive. There are still patches of ice/snow, mixed with wet road surfaces and tons of slush. And when the temperature drops below freezing again that night, the roads become patches of dry and black ice.

I often find myself driving down the road constantly shifting into and out of 4 wheel high range in these situations.

Am I doing something smart or am I being paranoid? I don't want my NP 231 to snap like a fortune cookie...

I've run mine for weeks on end at School on the icey mountain roads no problem. Just don't go over 50-55

I don't think you have to worry about it grenading. I have been told using 4wd on semi- dry pavement or dry payment will accelerate chain wear though.

There is no speed restriction when using 4hi. Although watch out when making turns if the pavement is dry.

Turns are those that killing NP231 or every Part time 4x4 on non slippery roads. In a straight line even in dry pavement there will be no problem other than less mileage and normal wear of the system.

I was driving onto the interstate from a rest stop, tractor and trailer already on the interstate goes sideways (he was in the left lane of three). His rig was touching both guardrails doimg about 60 MPH. Shortly before I'd shifted out of 4X, because the last stretch of road was dry, this stretch was snow packed. Picture me hitting the gas and praying for traction and acceleration. Everything worked out reasonably well, I hit a gap in the guard rail (I guess for service vehicles) doing kind of a power slide and got the truck out of the way. I did crumple a fender some.
Guy in my town bought an XJ, put it in 4X in October and made it till February before his 231 finally burnt up. I'm guessing he never bothered to read the owners manual.
I'm guessing dry road usage is a judgment call.
When in doubt I leave it in 4X, the way I always drove my 87, the transfer is still OK. I try not to overheat it, I stop every couple of hours and let things cool down. I check the fluid a couple of times a year. I usually change the fluid yearly (Dexron is cheap). The only part I've ever changed on the transfer was a rear tail piece (with new seal and bushing) and a front drive shaft output seal.

The XJ came with either the part-time np231 or the full-time np242.

The np-231 should only be driven in low traction situations. Wet pavement is not really low traction if you want long life from your np-231.

The best source for information on TC usage is your owners manual.

the biggest problem i see with the 231 and patches of ice or snow in the road is when the front and back wheels are slipping/spinning on that patch and the front leaves the patch and grabs the paved road while the back is still spinning. this may blow an axle or driveshaft ujoint or worst cast damage the transfercase.