Do I need an NP242 or better technique?

I have a bone stock 2001 XJ 4.0L with auto transmission and NP231 transfer case that I bought a year ago and I'm still learning about it.

I use it primarily as a DD but when we go camping/exploring I am often towing a small 1500# trailer to the campspot, then unhitch and go find some interesting dirt roads to explore. I drive those roads in order to go to interesting places -- scenery, views, old mines, ghost towns, whatever. I am *not* trying to find the worst road and see if I can make it through -- that's why the Jeep isn't lifted and I have no plans of doing so.

On a recent trip I was driving down a steep canyon that had a well-graded road of small rocks, and was in 3rd gear 4LO. The biggest problems were that 3rd was too fast -- I'm working on that -- and the fact that the front and rear driveshafts were locked together made the switchback turns very messy. The turns were tight enough that the steering wheel was all the way to the lock so I was getting a lot of cogging from the front axle U-joints. It was not only hard on the Jeep but it also tended to push me wider in the turns, and there wasn't much room to spare.

So I thought replacing the NP231 with an NP242 would take care of that problem, but I see that the NP242 has an open diff between the front and rear drivelines only when it is in 4HI - Full time, but not in 4LO. So it appears that with the NP242 I should use low gear and 4HI-Full Time in order to get around the switchbacks better.

I asked a friend about switching to 2HI just before the turns but he warned me that if I did so and found the turn so tight that I needed to back up, I would be stuck in 2HI and have poor traction while trying to back uphill. Sounds ugly to me!

So what, if anything, should I change on my XJ or in my driving to do a better job on a steep downhill road comprised of small loose stones and with many tight switchbacks?

Thanks!

With a 242, Part-Time should be used on 4x4 trails. The combination of differentials in both the 242 and the axles can often leave you stuck by spinning just one single tire.

No reason not to use 2wd as needed, and have the friend explain how the T-Case would get stuck in 2wd. Use 1/2 on the transmission if you need extra engine compression braking.

One might suspect that you need some new front axle u-joints instead of a 242.

Sounds like a Technique rather than an equipment fault. A FT case may help with the driving, but it isn't the cause.

Driving in the mountains towing a 1500 lb trailer is different than driving in the mountains. Unless your trailer has brakes, it will try and push the tow vehicle and you will go straight. Momentum is not your friend when descending hills with a trailer.

Take it easy though switchbacks. IIRC, the traffic going uphill has right of way, so going down you need to be mindful of that and think ahead. 3rd gear 4lo was probably too fast going into a steep narrow switchback. I usually don't speed though Off-Road switchbacks. Even without a trailer, I usually don't get above 1st (auto)-4Lo or 2nd-4Lo in a manual.

Speaking of trailers, make sure the load is balanced. If you put lots of tongue weight on the hitch, it will also affect the steering because you can lighten the front

I'm not sure I even understand how fast 3rd gear in lo is. 40 mph?

Tim_MN said:

With a 242, Part-Time should be used on 4x4 trails. The combination of differentials in both the 242 and the axles can often leave you stuck by spinning just one single tire.

Click to expand...

The road is well-graded, but is loose limestone rubble and 30% grades. In this specific case I would not expect a tire to lose adhesion. If I were on a road that I would lose adhesion of a tire on each axle I could always use the Part-Time.

Tim_MN said:

No reason not to use 2wd as needed, and have the friend explain how the T-Case would get stuck in 2wd. Use 1/2 on the transmission if you need extra engine compression braking.

Click to expand...

I have to let the Jeep roll a little bit to get the splines to line up in order to shift into 4wd, but there isn't much room to do so -- sometimes I have to try several times and I could run out of room.

Yes, 1/2 works in the sense that I currently always get 1, but that is soooo slow for what is a pretty good road except for the switchbacks. I expect to get the parts next week that will allow me to lock the transmission in 2nd gear whenever I want. That will help immensely with selecting the proper amount of engine braking, but won't do much about the messy tight turns.

Tim_MN said:

One might suspect that you need some new front axle u-joints instead of a 242.

Click to expand...

I have no sense of the U-joints binding, but like any U-joint, even those on a ratchet wrench, they cog when sharply angled. The switchbacks required the steering wheel to be at the lock if I wanted to get around the corner without backing up.

Thank you Tim for responding!

WB9YZU said:

Sounds like a Technique rather than an equipment fault. A FT case may help with the driving, but it isn't the cause.

Driving in the mountains towing a 1500 lb trailer is different than driving in the mountains. Unless your trailer has brakes, it will try and push the tow vehicle and you will go straight. Momentum is not your friend when descending hills with a trailer.

Take it easy though switchbacks. IIRC, the traffic going uphill has right of way, so going down you need to be mindful of that and think ahead. 3rd gear 4lo was probably too fast going into a steep narrow switchback. I usually don't speed though Off-Road switchbacks. Even without a trailer, I usually don't get above 1st (auto)-4Lo or 2nd-4Lo in a manual.

Speaking of trailers, make sure the load is balanced. If you put lots of tongue weight on the hitch, it will also affect the steering because you can lighten the front

Click to expand...

WB9YZU, thank you for responding!

I'm sorry I wasn't sufficiently clear that in this specific case I was not towing the trailer. I had only mentioned the fact that the Jeep is my DD and I tow a trailer so people would know I wasn't interested in turning the Jeep into a rig suitable only for off-road trails.

You are certainly right that 3rd gear was too fast, but currently my choices are only 1st and 3rd -- that will change as soon as the parts arrive that will allow me to use 2nd for engine braking as well.

You are also quite right about balance and brakes -- the second thing I did when I got the trailer was install a new axle with brakes. The first was new tires.

HappySlappy said:

I'm not sure I even understand how fast 3rd gear in lo is. 40 mph?

Click to expand...

Thanks for responding!

I don't know how fast it is either -- but it was too fast and I had to ride my brakes which meant I had to stop completely from time to time to let them cool down.

I was trying various things -- 4LO often was too slow, especially in 1st gear. 4HI and 1st gear wasn't a great choice either. 4LO and 3rd was the best choice but not really a great choice.

I would recommend either a RAdesigns shifter setup, or install a 2nd gear switch. Which enables you to use 2nd while in 1-2 position.

Johnnie Walker said:

I would recommend either a RAdesigns shifter setup, or install a 2nd gear switch. Which enables you to use 2nd while in 1-2 position.

Click to expand...

this is a good suggestion.

I've never had a problem engaging or disengaging 4Hi without moving, just put the trans in neutral. well, I just push in the clutch, but that's the point anyway.

In 4x4 on dry pavement, I would expect the front axle to have some binding (cogging ?) in sharp turns. Off-road not so much. I would also expect worn u-joints to have more binding then newer ones even off pavement. On any 4x4 trail I have been on, u-joint binding hasn't been an issue. Even Moab slick-rock gets run in 4 Low. I also have never had an issue shifting the T-Case and it not instantly engaging 4x4 Hi or Lo.

Johnnie Walker said:

I would recommend either a RAdesigns shifter setup, or install a 2nd gear switch. Which enables you to use 2nd while in 1-2 position.

Click to expand...

Yes, I'm working on that -- parts should arrive next week.

See http://www.naxja.org/forum/showpost.php?p=245787226&postcount=176 for more details.

Tim_MN said:

... I also have never had an issue shifting the T-Case and it not instantly engaging 4x4 Hi or Lo.

Click to expand...

Apparently I need to practice!

Now that I think about it, I typically have more problems shifting *from* 4HI to 2HI than shifting from 2HI to 4HI.

87manche said:

... I've never had a problem engaging or disengaging 4Hi without moving, just put the trans in neutral. well, I just push in the clutch, but that's the point anyway.

Click to expand...

I find on my rig that when I want to shift from 4HI to 2HI it works best if I am moving but with the transmission in neutral. If I am completely stopped there is often enough binding that I cannot move the TC shifter.

Tim_MN said:

In 4x4 on dry pavement, I would expect the front axle to have some binding (cogging ?) in sharp turns. Off-road not so much. I would also expect worn u-joints to have more binding then newer ones even off pavement. On any 4x4 trail I have been on, u-joint binding hasn't been an issue. Even Moab slick-rock gets run in 4 Low.

Click to expand...

The problem that I was experiencing is that on very sharp turns the difference in number of revolutions of the front wheels was so different than that of the rear wheels that it caused the Jeep to push the rubble with the front wheels and plow further to the outside the turn. Considering I wanted to make the turn as tightly as possible, this was counterproductive. It wasn't speed that was causing the understeer -- I was going slower than a walking pace.

I also hated the idea that I was messing up the nice grading by pushing the rubble around -- I far prefer to leave the road in no worse condition than I found it.

I have no experience with Moab slick-rock or the trails there -- are really tight turns common there?

Well if you're going downhill just use 2wd and put it in 1-2. Uphill use 4-hi. But it does spin like 4 full time would help. I have the 242 and prefer using full time when I'm on tight switch backs and I don't need 4lo. Just is easier on things and better on the ujoints up front

Here's the thing. You want to use your engine for braking as much as possible and not rely on your brakes so much in the mountains. As I mentioned, technique... I have never pushed though a corner in a switchback. If I feel binding, I back up a bit and take a different line. I may even decide that 4wd is not appropriate for the conditions.

IIRC, the standard 1/2 lock Change will work. The mod does work on OBD II controller but throws a code when engaged, as OBD II supervises the coils.
Also there is a modification by teraflex for the np231 to allow 2wd operation in 4lo. It disconnects the front output. You need to disassemble the case though. Useful in slickrock conditions.