'87 S10 4x4 trouble
First M. Lastname
stays on for the front wheels after shifting back to 2wd. The light
never goes out and it feels kind of like it's half engaged, but I don't
get the traction unless I move the selector to 4wd. What should I look
for?
- Pat pz...@omnibus.ce.psu.edu
Harvey Grubbs
FML> My pickup doesn't seem to want to come out of 4wd. The indicator light
FML> stays on for the front wheels after shifting back to 2wd. The light
FML> never goes out and it feels kind of like it's half engaged, but I
FML> don't get the traction unless I move the selector to 4wd. What should I
FML> look for?
According to my '85 shop manual, the 4 wheel drive is activated by
a vacuum actuator that is controlled by a cable. You may have a
problem with either of these. The cable may be out of adjustment
or the actuator may be defective.
... Dec 25, 1994. It's 14:01:03 in Atlanta.
---
. Blue Wave/QWK v2.12 .
ThomasL586
Lastname) writes:
The 4wd on S-blazers engages in 2 parts....the floor shifter changes gears
in the transfer case through direct linkage while there is a vacuum switch
that controls a servo to lock in the front hubs. What is probably
happening is that this vac switch is misadjusted/broken causing the front
hubs to remain engaged while in 2wd. Try looking at the vacuum
controls/hoses for trouble. Once you've corrected this, the indicator
light should work as well. When the front hubs are engaged in 2wd, the
truck will drive as if you are lightly riding the brakes (esp. when
turning tight corners) if the 4wd were engaged, it would "hop" in a tight
corner due to all 4 wheels being forced to rotate at the same speed
through circles of different circumference (this is why transfer cases
tend to disintegrate when 4wd is used on dry pavement).
Good luck!
Andrew MacPherson
: -=> Quoting First M. Lastname to All <=-
: FML> My pickup doesn't seem to want to come out of 4wd. The indicator light
: FML> stays on for the front wheels after shifting back to 2wd. The light
: FML> never goes out and it feels kind of like it's half engaged, but I
: FML> don't get the traction unless I move the selector to 4wd. What should I
: FML> look for?
: According to my '85 shop manual, the 4 wheel drive is activated by
: a vacuum actuator that is controlled by a cable. You may have a
: problem with either of these. The cable may be out of adjustment
: or the actuator may be defective.
My dad's Chevy 1989 Chevy S-10 had this vacuum actuator replaced twice in the
three years and 60K miles that he had it. He only used his 4WD in the winter,
and even then maybe once or twice a week. I wondered if it wasn't due to lack
of use that the actuator failed twice.
(as an unrelated aside:
the rear ABS on this truck would only work
for about 2 weeks at a time: then the dump valve would fail, and the module had
to be unplugged until it could be replaced (to make the ABS light go out.)
After replacing the valve twice and the module once, the local GM garage had
to wait 4 months before getting a replacement: presumeably because the part had
been re-engineered. He traded the truck on a 93-S10 (with 4.3L, but auto :( )
before the order came in. ABS works fine on the 93 :) Does anyone else have
problems with rear ABS on their pre 90 S-10s? )
: ... Dec 25, 1994. It's 14:01:03 in Atlanta.
: ---
: . Blue Wave/QWK v2.12 .
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JAMES LASHLEE...UNIV101-016
wheeling he had to back up about ten feet to get the automatic hubs to
disengage. When they did they made a distinctive clicking sound. You said that
the light dosen't go off, what about when you shut off the truck? Just
wondering, becasue I know that it may just take a few minutes to shut off due
to the engaging mechanism.
James
ter...@sfsc.com
>From: use...@psu.edu (First M. Lastname)
>Subject: '87 S10 4x4 trouble
>Date: 25 Nov 1994 16:51:55 GMT
You might want to check first if the 4wd is indeed disengaing or not.
Maybe jack it up on 4 wheels and see. If it is engaging, it may be that
the switch that senses where the 4wd lever is (or switches) is jammed and
lights the light all the time.
Jesse Hartley
George Forsman
>-=> Quoting First M. Lastname to All <=-
>
>FML> My pickup doesn't seem to want to come out of 4wd. The indicator light
>FML> stays on for the front wheels after shifting back to 2wd. The light
>FML> never goes out and it feels kind of like it's half engaged, but I
>FML> don't get the traction unless I move the selector to 4wd. What should I
>FML> look for?
>
>According to my '85 shop manual, the 4 wheel drive is activated by
>a vacuum actuator that is controlled by a cable. You may have a
>problem with either of these. The cable may be out of adjustment
>or the actuator may be defective.
>
be a hose that runs from the top of the transfer case (from the vacuum
switch mounted there) to the front right fender (between the fender and the
battery). This doubles as the transfer case vent hose, so clogging is a
possibility.
The way it works is that the front propeller shaft is disengaged at both
ends. When you switch to 4x4, you engage the xfer case end, and actuate a
vacuum switch which operates a diaphram actuator (under the battery). The
vacuum is fed through an oriface to delay the front diff clutch so that the
propeller shaft and the axle will be running roughly the same speed when
the clutch engages (so don't engage when on jackstands, or when your rear
tires are spinning!)
On mine, this happened for a while, but seems better now. At first it would
neither engage nor disengage, and that turned out to be a broken vacuum switch.
To disengage it, I have to slow down a bit, and I think that it's just the
clutch in the front diff getting stuck when there is a force against it from
the rotating axles.
My vehicle is a '90 1/2 s10 blazer, but GM did not change much over the years
(till '95, at least) so hopefully this info will help you.
--
George Forsman|geo...@microsoft.com | "I know that you think you understand
MSDOS Support |uunet!microsoft!georgef| what you thought I said, but I am not
--------------------------------------| sure you realize that what you heard
Disclaimer: Ask me! I'll deny it! | is not what I meant."
Disclaimer^2: The statements in this message are my own, not Microsoft's.
Henry H Hansteen
: My pickup doesn't seem to want to come out of 4wd. The indicator light
Henry
acss...@eku.acs.eku.edu
> My pickup doesn't seem to want to come out of 4wd. The indicator light
If this is a temporary condition (lasts only a few feet or a hundred
feet)... ignore everything I say below. It's normal. You can help it
come out by backing up or by jockying the steering wheel back and forth
a few times. All things that need to release are bound up by stored
torsion in the driveline and they will disengage as soon as the torsion
is relieved.
> - Pat pz...@omnibus.ce.psu.edu
Otherwise...
The parts involved are the switch for the lights that indicate what the
transfer case is doing... 2, 4Hi, N, 4Lo. The axle disconnect...
enguages the differential via a cable actuated by a vacuum servo motor.
And the linkage that activates the front drive shaft in the
transfercase.
My first *guess* is that your truck is releasing the transfer case, but
not releasing the differential. Out under the hood probably right behind
the battery is the vacuum servo motor. It looks exactly like the thing
that works the throttle when you are on cruise control. I would suspect
that either there is a problem with it's function (vacuum leak) or that
the cable that it operates may be sticking, or that something in the
axle disconnect is sticking. You can try operating the vacuum servo
motor by hand and see if that makes a difference. Just squeeze it in a
way that pulls on the cable. Do this with the engine turned off. You
should hear a noticeable click at the differential if you release it by
hand.
It could also be that the exact opposite is true. Your transfer case may
be stuck and your diferential may be free. If your transfer case whines
when your light says it's in 2wd? Most S10s will whine noticeably in
either 4Hi or 4Lo, but not in 2wd.
The confusing part of your description is that it shouldn't feel half
engaged if you don't have the additional traction. It's the binding of
the front and rear driveshafts *AND* the engagement of the front
differential disconnect that provides the traction and any feeling of
engagement. One without the other shouldn't make *much* difference. But if
either one could make a difference by itself it would likely be the
differential disconnect.
One way to know for sure, is to jack up the front end when it's in this
condition (selector set to 2WD and 4WD lights still on). Set the parking
brake and try to turn the front driveshaft by hand. If it won't turn, it
is because it is connected to the rear driveshaft and hence the parking
brake. If it does turn, you know the transfercase selection is working.
Also if the drive shaft turns, does either or both front wheel turn? If
only one turns can you make the other turn by stoping the one that's
turning with your hands? If so the differential disconnect is enguaged
for 4WD.
dsc
Dudley Cornman - Systems Programmer
Academic Computing Services
Eastern Ky. University
Richmond, KY 40475-3111
(606) 622-1986
Tom Forst
Forsman) writes:
[Stuff about 4WD not disengaging on 87 S-10] ........ I had an 86
S-10 Blazer for 130K miles. During that time I had to have the vacuum
switch replaced twice for just the reasons described. It was not
expensive, about $20.00. Mine also felt half-engaged until it was fixed.
One mechanic showed me how to manually dis-engage the front wheels by
removing the vacuum hose from the diaphram motor in the engine
compartment. The hose had to be plugged, of course, so that there
wouldn't be a vacuum leak. This also disabled 4 wheel drive, and was just
a temporary measure to allow driving the vehicle until the problem could
be fixed. The dealer gave me the old switch and it was abviously
sticking..
acss...@eku.acs.eku.edu
> In article <3b54nb$19...@hearst.cac.psu.edu>, use...@psu.edu (First M. Lastname) writes:
>> My pickup doesn't seem to want to come out of 4wd. The indicator light
>> stays on for the front wheels after shifting back to 2wd. The light
>> never goes out and it feels kind of like it's half engaged, but I don't
>> get the traction unless I move the selector to 4wd. What should I look
>> for?
>>
>> - Pat pz...@omnibus.ce.psu.edu
> My father had an 89 Chevy 2500 Subrban that was a 4X4. When ever we finished
> wheeling he had to back up about ten feet to get the automatic hubs to
> disengage. When they did they made a distinctive clicking sound. You said that
An '89 Burb uses an entirely different 4WD system from any of the
S-vehicles. S-vehicles don't require backing up in most cases although
backing up will work all the time. S-vehicles aren't known for any
noises when disengaging 4WD.
> the light dosen't go off, what about when you shut off the truck? Just
> wondering, becasue I know that it may just take a few minutes to shut off due
> to the engaging mechanism.
On S-vehivcles the light ususally goes off as soon as the axle
disconnects release.
First M. Lastname
of the transfer case (the one with 3 vacuum hoses attached to it.) Cost
$22 to fix. Not very difficult and it's a very common problem with
S10's and S15's.
- Pat Besong pz...@cde.psu.edu