Blazer autotrac

louisjohn · 06-04-2007, 01:18 PM

Can anyone help an old U.K. Blazer owner. My 2000 Blazer has only done 30000 miles. It is now unsupported by Chevrolet in this country, so I have to do all the work myself. I have had both rear caliper seize on me, I replaced these with rebuilds. I now have a problem with the autotrac system, some time ago the service 4-WD light came on. On restart the light went off and the system worked normally. The service 4-WD light has come on occasionally. Today the light came on again, and I find that the Auto 4-WD does not come on. Engaging 4h and 4l will sometimes work. I am pretty certain that the transfer case is OK, no unusual noises etc. Can anyone help this old Brit with good advice?

muslhed · 06-04-2007, 01:50 PM

I don't think the problem is with the x-case at all. Sounds like your front diff is not engaging, possibly due to a seized front diff cable. Read this post for more info:

ZR2 USA -> S-10 Front Diff & Posi-Lok Operation Explained

louisjohn · 06-09-2007, 01:00 PM

Thanks for info, very helpful. My gut reaction is a vacuum problem, by the way the system is acting.
I came across Country By Net.com, and there is a lot of similar discussion there, but it is focused around the switch module. It seems that the PCB developes cracked posts, these give similar symptoms. I understand with a clever bit of soldering the pins can be reattached!
Have you any further thoughts and advice on where I should initially start looking

louisjohn · 06-12-2007, 02:19 PM

muslhed
I am not sure about the vacuum line now. I find if the system does not work when the dash control buttons are pushed, that if I gently press the body of the control module around the buttons, that the system works perfectly. This is now leading me to suspect the P.C.B. in the swith module, as advised on the CountryByNet site. You can hear the transfer box shift from 4H to 4L quite distinctly. Also selecting 4H you can hear the sliding clutch in the front axle engage. I will keep experimenting to try and firmly establish the cause of the problem. What advice can you give at this stage?
By the way Grat Pics!
Louisjohn

muslhed · 06-13-2007, 08:55 PM

Quote: Originally Posted by louisjohn

muslhed
I am not sure about the vacuum line now. I find if the system does not work when the dash control buttons are pushed, that if I gently press the body of the control module around the buttons, that the system works perfectly. This is now leading me to suspect the P.C.B. in the swith module, as advised on the CountryByNet site. You can hear the transfer box shift from 4H to 4L quite distinctly. Also selecting 4H you can hear the sliding clutch in the front axle engage. I will keep experimenting to try and firmly establish the cause of the problem. What advice can you give at this stage?
By the way Grat Pics!
Louisjohn

Louisjohn,

I honestly have not heard of what you are describing before. I think the absolute best solution would be do as I am about to do.......and that is to remove all the electronic junk, and replace it with a manually shifted NP-231 from a 94-97 S-10 4x4. Pull a floor mounted lever, and the transfer case is engaged. Period. Install the Posi-Lok cable, and by pulling the cable, the front diff is manually engaged. Problem solved!

I gave up on trying to research all the issues associated with the GM electronically shifted NP-233 & NP-236 Autotrac transfer cases, a long time ago. Sorry I cannot be of more help on this one.

louisjohn · 06-15-2007, 09:29 AM

Muslhed,
Thanks for info. I will see if the part is available in the U.K. via the Ampar network
Johnlouis

06-04-2007, 01:18 PM	#1
louisjohn Registered User Age: 72 Join Date: Jun 2007 Posts: 4 Location: User is: OffLine	Blazer autotrac Can anyone help an old U.K. Blazer owner. My 2000 Blazer has only done 30000 miles. It is now unsupported by Chevrolet in this country, so I have to do all the work myself. I have had both rear caliper seize on me, I replaced these with rebuilds. I now have a problem with the autotrac system, some time ago the service 4-WD light came on. On restart the light went off and the system worked normally. The service 4-WD light has come on occasionally. Today the light came on again, and I find that the Auto 4-WD does not come on. Engaging 4h and 4l will sometimes work. I am pretty certain that the transfer case is OK, no unusual noises etc. Can anyone help this old Brit with good advice?
	[Reply w/Quote]

06-04-2007, 01:50 PM	#2
muslhed Registered User Age: 34 Join Date: Jan 2004 Posts: 33 Location: Ft. Worth, TX User is: OffLine	Re: Blazer autotrac I don't think the problem is with the x-case at all. Sounds like your front diff is not engaging, possibly due to a seized front diff cable. Read this post for more info: ZR2 USA -> S-10 Front Diff & Posi-Lok Operation Explained
	[Reply w/Quote]

06-09-2007, 01:00 PM	#3
louisjohn Registered User Age: 72 Join Date: Jun 2007 Posts: 4 Location: User is: OffLine	Re: Blazer autotrac Thanks for info, very helpful. My gut reaction is a vacuum problem, by the way the system is acting. I came across Country By Net.com, and there is a lot of similar discussion there, but it is focused around the switch module. It seems that the PCB developes cracked posts, these give similar symptoms. I understand with a clever bit of soldering the pins can be reattached! Have you any further thoughts and advice on where I should initially start looking
	[Reply w/Quote]

06-12-2007, 02:19 PM	#4
louisjohn Registered User Age: 72 Join Date: Jun 2007 Posts: 4 Location: User is: OffLine	Re: Blazer autotrac muslhed I am not sure about the vacuum line now. I find if the system does not work when the dash control buttons are pushed, that if I gently press the body of the control module around the buttons, that the system works perfectly. This is now leading me to suspect the P.C.B. in the swith module, as advised on the CountryByNet site. You can hear the transfer box shift from 4H to 4L quite distinctly. Also selecting 4H you can hear the sliding clutch in the front axle engage. I will keep experimenting to try and firmly establish the cause of the problem. What advice can you give at this stage? By the way Grat Pics! Louisjohn
	[Reply w/Quote]

06-13-2007, 08:55 PM	#5
muslhed Registered User Age: 34 Join Date: Jan 2004 Posts: 33 Location: Ft. Worth, TX User is: OffLine	Re: Blazer autotrac Quote: Originally Posted by louisjohn muslhed I am not sure about the vacuum line now. I find if the system does not work when the dash control buttons are pushed, that if I gently press the body of the control module around the buttons, that the system works perfectly. This is now leading me to suspect the P.C.B. in the swith module, as advised on the CountryByNet site. You can hear the transfer box shift from 4H to 4L quite distinctly. Also selecting 4H you can hear the sliding clutch in the front axle engage. I will keep experimenting to try and firmly establish the cause of the problem. What advice can you give at this stage? By the way Grat Pics! Louisjohn Louisjohn, I honestly have not heard of what you are describing before. I think the absolute best solution would be do as I am about to do.......and that is to remove all the electronic junk, and replace it with a manually shifted NP-231 from a 94-97 S-10 4x4. Pull a floor mounted lever, and the transfer case is engaged. Period. Install the Posi-Lok cable, and by pulling the cable, the front diff is manually engaged. Problem solved! I gave up on trying to research all the issues associated with the GM electronically shifted NP-233 & NP-236 Autotrac transfer cases, a long time ago. Sorry I cannot be of more help on this one.
	[Reply w/Quote]

06-15-2007, 09:29 AM	#6
louisjohn Registered User Age: 72 Join Date: Jun 2007 Posts: 4 Location: User is: OffLine	Re: Blazer autotrac Muslhed, Thanks for info. I will see if the part is available in the U.K. via the Ampar network Johnlouis
	[Reply w/Quote]