4x4 help needed
#1
12-28-2011, 12:39 PM
4x4 help needed
I have a 1992 full size blazer. I can't seem to get 4 lo or 4 hi to engage. Now I had the truck up off the ground to make sure it was not engaging and the front tires were not spinning at all. I know the transfer case is in engaging and I can hear the front axle actuator engaging and I e en took it out and made sure it was working properly which it was. So why is my 4x4 not engaging. Pease help winter is coming fast and I need this truck fixed. If you need any more information please just ask.
#2
12-28-2011, 01:14 PM
From your description, the transfer case is engaging 4HI & 4LO properly, but your front axle is not. If you have the stock thermal front axle actuator, that is likely your problem. GM released an update to an electric motor driven front axle actuator some time ago to upgrade the problematic thermal units. The problem with them is that they can operate perfectly fine off the front axle (albeit very slow), but be too weak to properly engage the front axle. And being thermally actuated, their response slows to a crawl when it's cold outside!
The upgrade requires a new harness(PN# 88959465) as well. An older version of this TSB makes reference to Z-harness PN 15313272 for the 88-93 models without the 4L60E transmission which have a front axle solenoid switch located right near the front axle engagement actuator. You may want to check with your local chevy dealer parts counter for updated part number references.
Dorman has these parts as well. PN 600-600 for the wiring harness & 600-101 for the updated actuator.
Upgrade kits which include the harness and updated actuator can be found on eBay for around $125 delivered.
For the 93 and prior vehicles, the additional wire in the harness gets spliced into CKT 50 (brown) between connector C171 & C173 (see attached wiring diagram).
Technical Service Bulletin
File In Section: 4 Drive Axle
Bulletin No.: 76-43-01A
Date: September, 1998
Subject:
Slow or no Engagement of Front Axle when 4WD is selected (Replace Front Axle Actuator)
Models:
1988-97 Chevrolet and GMC K Models
excluding 1988-93 Models over 8500 # GVW
This bulletin is being revised to add information to the Service Procedure, add a new part number, and include schematics. Please discard Corporate Bulletin Number 76-43-01 (Section 4 - Drive Axle).
Condition
Some owners may comment that the colder the outside temperature is, the longer it takes for the front axle to engage when 4 wheel drive is selected, or the front axle does not engage.
Cause
The front axle engagement actuator is a thermally activated component. Because of this characteristic, the time required for the actuator to complete 4 wheel drive engagement is extended as the temperature drops.
Correction
Replace the front axle actuator and include the applicable wiring harness kit. Refer to the Parts Information in order to determine which wiring harness kit is needed.
1996 model trucks with a build date on or after January 2, 1996 are considered as "961". If the build date of the truck is unknown, verify the 3 character "axle code" on the front axle label in order to determine which wire harness to order.
This new actuator uses a motor to engage the front axle and is not affected by temperature. On 1988-93 models with a GVW rating over 8500$, the new actuator cannot be installed and the thermal actuator will remain the service part.
26060073 Actuator Asm, Frt Drive Axle 1
Remove or Disconnect
Skid plate (if equipped).
Electrical connector from the indicator switch located on the upper right side of the differential.
Indicator switch (11).
Install or Connect
Indicator switch (11).
Coat the switch thread with sealer (GM P/N 1052942) or equivalent.
Electrical connector.
Skid plate (if equipped).
File In Section: 4 Drive Axle
Bulletin No.: 76-43-01A
Date: September, 1998
Subject:
Slow or no Engagement of Front Axle when 4WD is selected (Replace Front Axle Actuator)
Models:
1988-97 Chevrolet and GMC K Models
excluding 1988-93 Models over 8500 # GVW
This bulletin is being revised to add information to the Service Procedure, add a new part number, and include schematics. Please discard Corporate Bulletin Number 76-43-01 (Section 4 - Drive Axle).
Condition
Some owners may comment that the colder the outside temperature is, the longer it takes for the front axle to engage when 4 wheel drive is selected, or the front axle does not engage.
Cause
The front axle engagement actuator is a thermally activated component. Because of this characteristic, the time required for the actuator to complete 4 wheel drive engagement is extended as the temperature drops.
Correction
Replace the front axle actuator and include the applicable wiring harness kit. Refer to the Parts Information in order to determine which wiring harness kit is needed.
1996 model trucks with a build date on or after January 2, 1996 are considered as "961". If the build date of the truck is unknown, verify the 3 character "axle code" on the front axle label in order to determine which wire harness to order.
This new actuator uses a motor to engage the front axle and is not affected by temperature. On 1988-93 models with a GVW rating over 8500$, the new actuator cannot be installed and the thermal actuator will remain the service part.
26060073 Actuator Asm, Frt Drive Axle 1
Remove or Disconnect
Skid plate (if equipped).
Electrical connector from the indicator switch located on the upper right side of the differential.
Indicator switch (11).
Install or Connect
Indicator switch (11).
Coat the switch thread with sealer (GM P/N 1052942) or equivalent.
Electrical connector.
Skid plate (if equipped).
Dorman has these parts as well. PN 600-600 for the wiring harness & 600-101 for the updated actuator.
Upgrade kits which include the harness and updated actuator can be found on eBay for around $125 delivered.
For the 93 and prior vehicles, the additional wire in the harness gets spliced into CKT 50 (brown) between connector C171 & C173 (see attached wiring diagram).
Last edited by swartlkk; 12-28-2011 at 01:50 PM. Reason: EDIT to add info & part numbers.
#3
12-28-2011, 04:00 PM
I do have to upgrade to the electric actuator. I have done everything you listed by buying the wire harness and spicing the brown wire in. I previously did this awhile ago. I still can't figure out why the 4wd will not engage
#4
12-28-2011, 04:10 PM
If you already have upgraded the actuator and it is working properly, then there is a problem inside the front axle. You will have to remove the passenger side extension housing and inspect the shift fork & collar.
#6
04-16-2012, 09:00 AM
When I inspect the shift to and collar what should I look for. Also do you have any suggestions or tips for taking apart the passenger side?
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