four wheel drive problems

ddraszt · 12-15-2007, 06:39 PM

99 gmc sierra 1500 5.3 4x4 z71
hey i am having an issue and hoping someone can help. my four wheel drive is not working properly. It worked when I bought the truck a few months back but had not been used til a few weeks ago. I was in the snow and it wouldn't go which was not fun. I checked and the front driveline was spinning so a replaced I replaced the front axle actuator assuming the axles weren't locking in and took it for a test drive to a gravel parking lot. Initially it seemed to engage (usually you can tell by the tire grip. Then it made a couple klunk or hard popping noises from the axle or transfer case area and no longer felt as if I was in four wheel. I am wondering if this seems like an issue in the front axle or maybe the clutch in transfer case ( some research has indicated it has one) or anything else. Has anyone had this problem? Please help. Thanks.

shoman44 · 12-16-2007, 06:30 AM

is your 4wd service light on?

shoman44 · 12-16-2007, 06:31 AM

also do u have a 4wd lever or push button?

75K30 · 12-16-2007, 10:18 AM

You could simply have a bad switch, (not uncommon) or a bad controller that is telling the truck to dis-engage.
The controller is the device that provides the vacuum signal to the actuator.
These can really freak out from time to time, and stories of 2wd engaging randomly at highway speeds are not rare.
Unless you hava an AWD system you t-case should only have a chain, and no clutches. The output from front to rear has an equal split. This means that your case is probably alright.

nordy · 12-16-2007, 11:31 AM

Definitly replace your vacuum actuator. It's easy to replace, mine only cost $20.

75K30 · 12-16-2007, 01:08 PM

Quote:

Originally Posted by nordy

Definitly replace your vacuum actuator. It's easy to replace, mine only cost $20.

Think the OP already did that. He stated that the actuator was replaced when the front axle would not engage.

ddraszt · 12-17-2007, 07:09 AM

sorry for not clarifying. It is equipped with the push button four wheel drive and does have the part time four wheel drive option. The acuator is a thermal solenoid that threads into the diff which is what i replaced. I do not see any vacuum lines. The lights on the switch indicated what you are in 2hi/parttime/4hi/4lo as they shoul. I have been told that when those switches go bad it will revert back to 2hi when trying to switch. There is no service lights. I was reading somewhere that there was actually a clutch in this tcase. Don't know for sure.

mudseeker · 12-17-2007, 07:14 AM

this is the reason i don't own a truck with the push button option, not very reliable.

MORROWMUDDER · 12-17-2007, 08:42 AM

im actually having the same problem with mine right now, just started doing it a couple weeks ago when i was in the mountains going for a ride, when i needed it, it did'nt want to go in. im so fed up with working on the **** thing i just said the **** with it. if it breaks it breaks, then at least i'll know what to fix and take the guess work out of it!!

12-15-2007, 06:39 PM	#1
ddraszt Full Member Join Date: Jun 2007 Location: arlington wa Posts: 43	four wheel drive problems 99 gmc sierra 1500 5.3 4x4 z71 hey i am having an issue and hoping someone can help. my four wheel drive is not working properly. It worked when I bought the truck a few months back but had not been used til a few weeks ago. I was in the snow and it wouldn't go which was not fun. I checked and the front driveline was spinning so a replaced I replaced the front axle actuator assuming the axles weren't locking in and took it for a test drive to a gravel parking lot. Initially it seemed to engage (usually you can tell by the tire grip. Then it made a couple klunk or hard popping noises from the axle or transfer case area and no longer felt as if I was in four wheel. I am wondering if this seems like an issue in the front axle or maybe the clutch in transfer case ( some research has indicated it has one) or anything else. Has anyone had this problem? Please help. Thanks. __________________ "It is what it is"

12-17-2007, 07:09 AM	#7
ddraszt Full Member Join Date: Jun 2007 Location: arlington wa Posts: 43	sorry for not clarifying. It is equipped with the push button four wheel drive and does have the part time four wheel drive option. The acuator is a thermal solenoid that threads into the diff which is what i replaced. I do not see any vacuum lines. The lights on the switch indicated what you are in 2hi/parttime/4hi/4lo as they shoul. I have been told that when those switches go bad it will revert back to 2hi when trying to switch. There is no service lights. I was reading somewhere that there was actually a clutch in this tcase. Don't know for sure. __________________ "It is what it is"

12-17-2007, 07:14 AM	#8
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,374	this is the reason i don't own a truck with the push button option, not very reliable. __________________ i'd rather be hunting

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12-16-2007, 06:30 AM	#2
shoman44 Junior Member Join Date: Dec 2007 Posts: 17	is your 4wd service light on?

12-16-2007, 06:31 AM	#3
shoman44 Junior Member Join Date: Dec 2007 Posts: 17	also do u have a 4wd lever or push button?

12-16-2007, 10:18 AM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,992	You could simply have a bad switch, (not uncommon) or a bad controller that is telling the truck to dis-engage. The controller is the device that provides the vacuum signal to the actuator. These can really freak out from time to time, and stories of 2wd engaging randomly at highway speeds are not rare. Unless you hava an AWD system you t-case should only have a chain, and no clutches. The output from front to rear has an equal split. This means that your case is probably alright.

12-16-2007, 11:31 AM	#5
nordy Junior Member Join Date: Oct 2007 Posts: 8	Definitly replace your vacuum actuator. It's easy to replace, mine only cost $20.

12-17-2007, 08:42 AM	#9
MORROWMUDDER Senior Member Join Date: Mar 2007 Location: Ohio/Montana Posts: 138	im actually having the same problem with mine right now, just started doing it a couple weeks ago when i was in the mountains going for a ride, when i needed it, it did'nt want to go in. im so fed up with working on the ** thing i just said the ** with it. if it breaks it breaks, then at least i'll know what to fix and take the guess work out of it!!