Your 4WD System
Late Model FSJs
> 4WD high and 4WD high > 2WD
the vehicle in neutral, flip the SelecTrac switch, and if the 4wd
green lite doesn't come on, let off the brake. If that doesn't do
it, put the vehicle in reverse, then neutral, then drive. By this
time the vehicle should be in the desired drive mode. If not, try
rolling it forward or back a tiny bit.
also shift to/from 4wd: I flip the switch after letting up on the
gas, normally that does the trick, otherwise, shift into neutral.
I've shifted anywhere from 0-55mph with no problem.
> 4lo and 4lo > 4hi
-- must be in 4wd already (see above)
moving 0-2mph and be quick about it. I prefer shifting stopped.
If you grind, that's life stop the vehicle, turn it off,
leave in neutral and then shift. If you've got new fluid and you
get some practice you can shift while slowly rolling or when stopped.
Best not to be uphill or downhill when doing this or you're sure
to have to stop and turn off and maybe let the vehicle roll a bit
then stop and try again. If you shift and get the tcase in neutral
instead of the range (lo/hi) you wanted, at this point you might
as well shut it off to shift.
to use 4lo or 4hi?
In 4hi you can drive on any condition of road, pavement,
dirt, etc. Slick conditions such as snow or ice may warrant 4hi, if
you need to maintain highway speed. Off road if the trail is smooth,
flat, and wide where faster speeds can be safely achieved. Never drive
over 25mph on a tight trail with blind curves.
Only drive 4lo
off-road. Absolutely no dry pavement in 4lo!! Use 4lo for climbing
and descending steep hills. The low gearing actually helps as a
brake for descending steep inclines.
is Selec-Trac and Quadra-Trac?
QuadraTrac is what Jeep called the Borg Warner 1339
transfer case (and the 1330-something whatever the one was with no
lo-range). They also gave this label to the New Process 219. Both
are full-time 4wd systems. The BW1339 uses a viscous limited slip
that transfers powers from slipping wheels to gripping wheels whereas
the NP219 I believe is just a limited slip that uses a cone to prevent
what Jeep labeled the vehicles with NP228 and NP229 transfer cases
(probably others in the other models?) which shift gears by way
of a vacuum switch under the dash. These systems can operate in
2wd mode or full-time 4wd mode (i.e: drive on dry pavement in 4wd).
The NP228 (1986) has no limited slip; the NP229 uses a limited slip
similar to the NP219.
You may also
have heard of CommandTrac and QuadraTrac II, the former being associated
in my own pea brain with baby Wagoneers and Cherokees and is a shift-on-the-fly
part-time setup operated by a single lever (anyone know what tcase?)
The QuadraTrac II is the cool tcase optional in the brand new Grand
Cherokees the vehicles some of us will be driving afford
in 10-15 years when they become affordable and our FSJs are rotting
down to the frame.
The only relation
"SelecTrac" has to differential operation is this at some
point in the early 1980's (83? 82?) Jeep started using a vacuum
actuated axle disconnect in the D44 front axles, along with SelecTrac
in the form of the NP229. You couldn't shift on the fly; you had
to wait for the front axle to engage or disengage which coincided
with selecting 2wd or 4wd. I'm not sure on the details of which
models have this vacuum front diff. I am pretty sure this went away
in 1984 and certainly by 1985.