Jim,
On my 88 I had a similar problem. First thing to check is the bulb that
lights up the 4WD light by the transfer case shifter. Make sure it's really
not going into 4WD before you climb under the truck. Second, the Dakota's
shift on the fly system uses a vacuum powered shift motor assembly on the
front axle. It is located on the disconnect housing over towards the
passenger's side of the axle, right near where the CV bolts up. It's a round
assemble that has two vacuum hoses attached to it. It seems over a period of
non use, it will stick. Vacuum is given to one line when the truck is in 2wd
(this will disengage the front end), and to the other line when the truck is
in 4wd (to engage the front end). After locating the unit, start the engine
and then get under the truck and remove the vacuum lines. It only clips on if
I recall correctly. Check to see if you have vacuum to one line, shift the
truck into 4wd and check to see if it switches to the other line. If that
works correctly the problem is in the shift motor. I sprayed penetrating oil
into both vacuum tubes on mine and it seemed to free up for a while. It
started doing it again after a few months so I replaced it. You can tell when
it's acting up if it fails to engage when the truck is put in 4WD or fails to
disengage when put back into 2wd. If it fails to disengage, put the truck in
reverse and back up 15 ft. That will usually pop it loose.
Now on the other end of the two vacuum lines there is a vacuum switch on the
transfer case. It's in an awkward place so you really have to look. It
screws into the housing and has 4 vacuum hoses running to it. One of the
hoses runs to the black ball canister under there so if you don't see it
follow the lines from the canister. The unit itself looks similar to an oil
pressure switch. It's a rather simple switch. There's a button that
protrudes from the threaded neck. When the truck is in 2wd the button is out,
when you shift into 4WD a lever inside the transfer case will push it in.
That's the entire switch. This will sometimes stick in and the truck will not
disengage 4WD. You can tell if it fails by checking the vacuum to the front
like I said above. If the vacuum does not shift from one line to the other,
the problem is with this switch. If I recall correctly, both are like $20 or
$30 parts. It sounds like your problem is most likely with the front shift
motor.
http://www.geocities.com/MotorCity/Downs/9219
-----Original Message-----
From: James Babcock
Sent: Friday, September 05, 1997 8:33 AM
To: dakota@ait.fredonia.edu
Subject: Early Dak 4x4 Failure
I know that the front axle is a weak point in the early design of the
4WD, and it seems that mine does not engage. I'd like to fix this
before the snow starts flying. Can anyone tell me where to start
looking? TIA.
Jim
'87 V6 auto 4x4
-- James A. Babcock, Software Engineer email: james.a.babcock@adn.alcatel.com Alcatel Data Networks WWW: http://www.adn.alcatel.com Ashburn, Virginia USA phone: +1 703 724 2762 Support your local Habitat for Humanity chapter (http://www.habitat.org)
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