NP 231 to NP242, feasable?

[wavingpine11]

I like this discussion--very amusing. I'm amazed it has gone so far. I have the 242 case in my XJ and I installed an ox locker in the front to avoid having to negate the full-time position's usefulness and safety on moderately tractive surfaces. This is the key point--how much traction is present. In 2wd, before I installed the rear auto-locker, I would regularly experience the famous one-wheel-drive effect when starting out on freshly rain-covered roads. The rear locker prevents this from happening now.

The torque from the drive shaft is used to cause the cross pin to push the geared faces of the auto locker's gears tightly together, preventing them from differentiating. I think most of us would agree with this statement.

As we all know, differentiation is very useful feature provided on our axles as a convenience to those people who like to be able to turn their vehicles without having to break one of the tires free, or have something else break in its stead. There is a reason why very few people would think to spool the front of their DD, and since sending torque to the front diff with an auto locker makes it lock, you may as well have a spooled front because while enough torque is pushing the front to lock the unit, you are going to have all of the negative effects of being spooled, only worse, because it may unlock if you let off the gas enough, making handling unpredictable. Sure, plenty of people will spool the rear and live with it, but the front is pretty crucial to making an easy turn like 99.99% of the rest of the automobile owning public enjoys.

The point of the full-time system is that it is a great ON-ROAD system. On asphalt or concrete, unless it is snow or ice covered, in which case you'd want to be in part-time 4wd, you still have lots of available traction. Dividing the available torque from the transmission by 4 rather than 2 means that you break free less easily because you are effectively only sending about half the amount of torque to the rear tires vs. being in 2wd. Would you drive in full-time on solid ice? No--it would be useless one wheel drive all over again. Actually, before I had lockers in the current rig, I was out on an easy dirt trail in the winter. I had it in full-time unknowingly (I had driven to the trail that way) and got stuck on a basically flat part of the trail. It took a long time to work my way out, and, man, I felt stupid when I noticed afterwards that I was, in fact, in full-time rather than part-time 4wd where I would have at least been pushing two wheels rahter than one. Wet road is much more tractive than icy trail. Auto locker plus full-time 4wd on-road is just a bad idea. Goodburton gets it! I get it. . . Any dissenters want to climb on board and get it, too?

--wavingpine11

 

[winkosmosis]

So your point is that when they have even resistance you get even power distribution.. I get it. I know how a differential works.

But when push comes to shove only one wheel can take all of the power from the rest of the wheels in full time and in 2wd.

In part time one wheel in the front and one in the back (based on open diff's)

The force to the other wheel is only equal to the resistance of the slipping wheel divided by the number of differentiated wheels.

No the right one always is worn more.

But that's exactly what we're talking about... The 242 in full time mode in the pavement, which is exactly when the front wheels are receiving almost half the power coming out of the tcase. It's just not true that the rear wheels get all the power most of the time, which is what someone said to argue that the locker in front should be fine.

 

[winkosmosis]

For ice or gravel I'd rather have full time. In PT, you can feel one of the axles break loose when you steer. With FT, you still get the benefit of torque distributed 4 ways.

There's a reason drifters use limited slip diffs or even welded diffs... easier to break loose.

 

[ehall]

FT is going to better on ice if you are still moving, but if you stop PT is necessary

 

[Muddy Beast]

Wow this thread is full of so much bad info mixed with good info...I imagine it's incredibly misleading to a noob.

The rear bias is like 52% - 48%. The front wheels are always getting torque, the center diff has no choice. Just like both rear wheels are getting power in RWD mode. It's an old myth that an open diff is "one wheel drive".

^If this was referring to the how full-time works after taking into account what happens when a tire slips, Nominated.

~Scott

 

[winkosmosis]

Wow this thread is full of so much bad info mixed with good info...I imagine it's incredibly misleading to a noob.



^If this was referring to the how full-time works after taking into account what happens when a tire slips, Nominated.

~Scott

We're talking about on the STREET and the reason why you can't use full time with a lunchbox locker on the STREET. It doesn't matter whether the wheels all have traction, or you go over ice. Those front wheels are powered, which means the locker is working, which is BAD FOR THE STREET.

"1 wheel drive" implies that the drivetrain is always driving just one wheel. A lot of people really believe that because they see a wheel with no traction spining, but that is a false belief caused by ignorance of how a differential or open t-case works. If that were reality, you COULD use a lunchbox locker in the front with full-time mode, because only "one rear wheel is powered anyway" right? It would also mean that full-time 4WD is useless, which it obviously isn't.