My vehicle is a 99 jimmy with 4 button system.
Ok here is what happens, the truck starts out in 2hi I press the 4hi button,
I hear a click from the computer on the right side, now the 4hi button
continues to blink, it will continue to blink never switching back to 2hi,
now if I press the 4lo button the 4hi will stay on and the 4lo will come on,
but when I put it in gear only the rear end is in 4lo, the back tires will
spin in 4 lo but the front end has no power.
It is as if the valve in the front under the battery box isnt working or I
have a vaccum leak. Any suggestions?
If anyone posting BS its you Roy, I have the actual dealer manuals for
that model and others (exact same one/system dealer uses) I can even
look vehicals up by VIN here can you?
Hell, you can't even spell it. It is "vehicle" dick head. Now, why don't you
go back to the V10 thread at aadt and correct your totally wrong answer.
Then perhaps you can also answer the questions you were asked but chose to
Oh, I suppose I'll have to adjust your sig here as well. It was a big hit at
Sorry if I've offended anyone here. It is just this pos posting BS info is
Yes, it's obvious that the front diff is not engaging. There is a
switch in the front diff that closes when the fork that engages
the front axle moves into the "engaged" position. If the t/case
module does not see that signal, you will never get a shift into
Depending on the year, you either have a number of vacuum
lines running back to a switch that is on the drivers side of
the t/case. One will be vacuum supply, one will be a vacuum
line running to the vacuum motor sitting under the battery, and
one is a vacuum vent line. The first thing to do is see if you
have a good vacuum source to "that" switch on the t/case. If
not, you need to fix that (obviously)....if you do, then you have
to determine if the switch on the t/case is working...allowing
vacuum to the front diff vacuum motor. Eventually, you should
figure out where your problem is. Often, I'll start the other
way round, apply some vacuum to the motor under the battery
and see if the front diff engages....and work back from there.
The newer vehicles (and might include yours, can't remember) use
an electric over vacuum switch which is mounted to the firewall
right above the back of the intake manifold/distributor area. It
was a problem, so if you have "that" system, take off the two
vacuum lines, see if you have vacuum on one, if so, plug the
two lines together, if you now have the front diff engaged, the
switch is the problem.
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