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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #1
Good morning, and new member here.
I have an interesting dilemma. I own a 2000 GMC Sierra SLE, lately I have not been able to get my 4wd to activate.
I have replaced the dash switch, Axle Actuator as well as the TC motor.
I gave hear ad feel everything engaging, but when I jack the truck on place all four tires on jack stands, nothing upfront moves. the font axle shaft spins even when in 2hi?
I do not have any check engine lights or service fwd. The t-case was resealed last summer and was told everything looked good. All fluid levels as good in both the trans as well as the T Case.
the only thing I can think of is the TCCM, or something internal.
Can bad hub bearing prevent the front wheels from activating?
Any an all help would be appreciated

Memo
 

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Memo, when you ask for 4wd (using the switch), the shift motor is commanded into place by the control module (TCCM), when in place, the TCCM is advised, it them commands the front axle actuator to operate. When operated, a signal is returned to the TCCM, when then commands the clutch pack to engage.

Try checking and cleaning the contacts in the connectors, you may be missing one of the return signals.
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #3
Memo, when you ask for 4wd (using the switch), the shift motor is commanded into place by the control module (TCCM), when in place, the TCCM is advised, it them commands the front axle actuator to operate. When operated, a signal is returned to the TCCM, when then commands the clutch pack to engage.

Try checking and cleaning the contacts in the connectors, you may be missing one of the return signals.
Memo, when you ask for 4wd (using the switch), the shift motor is commanded into place by the control module (TCCM), when in place, the TCCM is advised, it them commands the front axle actuator to operate. When operated, a signal is returned to the TCCM, when then commands the clutch pack to engage.

Try checking and cleaning the contacts in the connectors, you may be missing one of the return signals.


Ray,

Thank you for the tip
I will take the TCCM module out and clean it out.
when I replaced the actuator an TC motor
I make sure I clean out the terminals an use Dielectric grease.
hopefully it is something as simple as cleaning out the terminals. One thing I forgot to mention was that I did in fact clean out the ground terminals underneath the driver side.
 

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Not talking about the terminals on the TCCM, talking about the connectors under the truck, at the transfer case and at the front actuator.
Did you buy a new shift motor?

Oh, and do not use grease on the contacts it is an insulator.
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #5
Not talking about the terminals on the TCCM, talking about the connectors under the truck, at the transfer case and at the front actuator.
Did you buy a new shift motor?

Oh, and do not use grease on the contacts it is an insulator.

Ray,

all components under the truck are new.
I will clean out the terminals later this week and re attempt to see if the 4wd function will work.
 

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Memo, just something I found on the net:

What is Dielectric Grease?
Posted on February 26, 2015 by Andrew Gardner
11
dielectric grease
Dielectric grease, or tune-up grease
, is a silicone-based grease that repels moisture and protects electrical connections against corrosion. It is also used to keep dirt, water, and other elements out of electrical connections. It has many uses, including automotive tune-ups, home electrical work, and recreational vehicle wiring. Dielectric grease does not dissolve in most liquids, so it is good for marine and outdoor applications. You can use this grease to lubricate the rubber parts of electrical connectors, spark plug wires, and to protect electrical connections on your boat or recreational vehicle from corrosion. Since dielectric grease is a silicone grease, it should not be used on silicone-based rubbers or plastics, as it will break them down over time. The grease does not conduct electricity, so it shouldn’t be applied directly to the mating surfaces (pins and sockets) of an electrical connection.
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Some added info:

The front driveshaft will spin in 2Hi. This changes back in the 03 trucks. My 00 Silverado does it.
 

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Ray,

all components under the truck are new.
I will clean out the terminals later this week and re attempt to see if the 4wd function will work.
on my vehicles I use silicone dielectric grease on the pins/contact electrical .. I have a 1996 and 2000 GM vehicles no electrical pin corrosion ... I buy new and put the silicone dielectric grease on the engine compartment connectors / pins .. in the rust belt that is a great protection.
also I use silicone brake grease on my caliper boots and piston seals .. my 1996 GM vehicle factory calipers working perfectly .. I also have a 1978 wellcraft 20ft .. no electrical problems ....
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #9
Thanks to all for the feedback.
Hopefully its something simple im over looking.
I'm contemplating replacing both from hubs, but I don't want to keep throwing parts at it unless it needs it.
 

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because it is an old truck you have to check the wiring from the fuse box to the transfercase. the harness had some members with the wiring insulation got damaged and the wiring should have a plastic cover over the wiring .. also some had encoders new not working .tricky on the install of the encoder...encoder has feedback electrical contacts so no codes but do you have a code reader that reads drive train/abs codes ...
my front drive shaft is most all the time locked to the front diff...could be the front actuator sticking and many had corrosion on those electrical connectors .. check the front diff .../ actuator remove it and see if it operates ..
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #11
J cat
prior to installing the new axle actuator I had my son press the dash switch to verify the actuator actually working.
The old one worked as well, but since I already had the bee one I swapped them out.
I saved both the dash switch and actuator as back up.
the only thing I did not test prior to installing was the TC motor since I did not want to damage it. But I can hear it engage as well as feel (place my hand on it will being engaged)

my code reader does not read drive train/abs codes
although I have no lights other than abs lights but thats another issue. even though I've replaced both speed sensors I get low speed abs activation sp I pulled the 60 amp fuse.

Memo
 

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if you put it in 4wd then a code will throw. then if you shutdown the engine key off the code will drop out..
go to a auto part store advance auto or auto zone to use the scan tool for the abs/drive train codes.. plug it in set it up then drive the truck then put it in 4wd .. code will throw and then post on here....
4wd codes are a bit / many .. then code will indicate where the failure is...
GM transfer case fluid is specific for your vehicle.. no transmission fluid dexron III/VI... color of the fluid is blue NOT red..
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #13
j cat
I will attempt the steps you mentioned
although I can verify that no codes are displayed
but none the less I will attempt an post here
 

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2000 Silverado Z71 4x4 5.3L 460k+ miles w/ GM rebuilt motor and trans
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Your hub assembly will not affect the 4wd. It is a straight spline gear. Either the front diff is in 4x4 or it's not. Unless you added manual locking hubs, this is not the right tree to bark up.
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #15 (Edited)
Opal
thank you for clarification
the only other thing I can come up with is the TCCM or internal. I guess I'll have to wait till I can take it I. tk the trans shop on Monday.
luckily I don't need 4wd at the moment and for when I do I have my 83 k5 Blazer for that.
non the less I will post the outcome
 

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Memo, transfer case, abs, transmission, body codes will not light the CEL, usually just a message in the DIC, but there will be a code.
As Jacob said, the hubs will not cause any 4wd issues, however, they will cause ABS problems.
By the same token, ABS problems will not cause any 4x4 problems.
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #17
Ray or anyone

What would be a good recommendation for code scanners. The one I have is a generic one that will read / erase codes only.
hopefully I can find one with all these holiday sales going on.
 

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Hi Memo43,
I’ve had similar problems with my 4wd on my ‘05 Avalanch LTZ71. Had both the Trans. And the Transfer case replaced about 2 years apart and thought maybe the warranty on the swap outs might help cure my problem. Guy that did the work talked with me and said to try replacing the ignition switch. That’s where he starts his troubleshooting. We had a 2,000 mile gap (my truck to his shop) at the time, so I tried his suggestion. Best $35, 20 minute fix I ever had. Basic understanding here is every time you turn the key that activates the ignition switch which powers up all kinds of system in the vehicle. And they get old and weaken to the point that they only kinda pass enough current to activate everything. A new ignition switched worked for me.
 

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2000 Gmc Sierra 1500 sle 4wd
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Discussion Starter #20
tha name for the tip
Rperry I'll look into it, my ignition cylinder can be finicky to turn the key.
That's the part you are referring to correct
the key cylinder or the switch under the column.

hope everyone had an awesome Thanksgiving

memo
 
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