your advise to my heating problems was good. Thanks.."Doc" and "Ian"
Now it seems the 4x4 is not working. When I press the button on the dash I
here something clicking in underneath but as I steer hard left or right on
dry pavement it feels the same as in 2wheel hi. Shouldn't there be some
rough tire vibration or skipping as I turn slowly? Also there is a
plug(switch) broken off that screws into the actuator on the front diff .
I've purchased a new one at the Dealer( switch: $ 30.00) but haven't got
around to installing it. Could I be so lucky that this is all it could be ?
Is there other things I should know about or look for?
P.S. A GM mechanic told me that in changing diff oil if the fill plug
doesn't come out due to corrosion, they drain the diff fluid , take it
apart, then throw in zip-lock bags full of Diff fluid in and close it all
up. He says eventually the plastic zip-lock bag disintegrates. Has anyone
ever heard of this method?
The switch on the front diff on your vehicle is simply a feedback
switch that tells the 4x4 module that the differential has achieved
engagement. When you say that you are getting clicking sounds,does
the mode light change (does it switch from the 2hi light to the 4hi
light). If not, try this: Use a jumper wire and jump terminal 13 on
the DLC connector under the dash...to ground (with ignition off). Then
turn on the ignition and observe the 4x4 dash switch lights...they should
begin to blink out codes. It's similar to way the old engine codes were
read, if you have say....code 2...the light will blink twice and then pause,
then blink twice again...and keep repeating this until the jumper wire
is removed. I'm going to guess that you will find code 2 in the system.
This is an indicator that something is wrong with the encoder motor and/or
wiring to it.
Now what you do, is......turn off the ignition, remove the 10 amp CTSY LP
fuse (open the drivers door, you will see the fuse panel, left side of the
facing the door) and leave it out for 2-3 minutes. Re-install the fuse,
ignition key to the run position and then off, 5 times. This will clear a
that is automatically set when you remove the fuse. Now attempt to perform
a 4x4 shift. If it works now, you need a new encoder motor. If it still
work, check for the codes again (jumper wire) and if code 2 is still there,
problem is most likely still the encoder motor, but it's a "hard" code. At
point, you can do the wiring checks before heading off to buy a new encoder
motor. My experience has been that it's almost "always" the encoder motor.
Oh yeah....put that broken switch in before you do any of the above.
I've heard of it, but this strikes me as real chicken-shit mechanics.
We run into this problem and we always manage to get the fill
plug out and put a new one in. That's what drills, air chisels...whatever
you need to get it out...are for.
Once again you are providing very intelligent and sound advice, Ian. I just
wanted you to know that the light on the dash does light up when changeing
over from 2hi to 4hi , everything on the inside seems to work as the manual
says it's supposed to work. I'm just wondering if to procede as per your
instructions on encoder motor?
No...if you are getting a solid 4hi light, it means the encoder motor has
performed it's shift (so the t/case is now in the 4hi range) and it has
seen a signal from the front diff that it has been actuated.
So let's review. As far as you can tell, it is shifting into 4hi, but the
front wheels are not engaged? Or are you saying that you followed
my instructions, pulled the fuse, cleared the code, and now everything
works fine? I'm not quite sure what you actually did.
If you did follow my instructions and cleared the code and now it
works fine....you can do one of two things, replace the encoder
motor....or just drive it and see if it screws up again. It all depends
on whether you are willing to risk having no 4hi at a most inopportune
Ian, I haven't done anything as per your instructions yet. The on dash push
button has lit up when going from 2hi to 4hi as well as the clicking sounds
underneath can be heard during this transition. however, I'm almost positive
the front wheels aren't getting any power because when turning hard left or
right on dry pavement shouldn't the front tires skip or vibrate?
Yes, you should feel the vehicle "crow hop". Maybe you need to
jack up the vehicle (all four wheels) and actually verify whether you
are getting power to the front axle. Probably best to do this before
we get involved in all sorts of diagnostics that have nothing to do
with whatever the real problem is.
Ok Ian I brought the truck to the dealer and when they attempted to install
that switch onto the black plastic triangular part attached to the side of
the diff , we discovered that (as they call it ) actuator rod through the
diff was busted . I seen it as the tech opened it up . I also made them run
the truck in 4hi while on the hoist just in case something would work but
So the final bill is around $700.00 ----The part is $112.00 and the rest is
labor, they tell me the entire diff has to be taken apart.
After all this I brought the truck to an independent tranny shop but they
are going to quote me a price tomorrow
What's your take Ian?
Without seeing it, it's hard to say. Usually when there problems
with the shift mechanism on the front differential, it's possible to
just take the extension tube off on the right side...you don't have
to actually take the whole diff out. But because I can't see what's
damaged....I'm not going to second guess the tech who did see it.
If the diff has to come out, it's pricey. These are not fun units to
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.