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1991 Gmc four wheel drive doesn't kick in Electrical?
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greg555
New User
Jul 8, 2008, 2:59 PM
Post #1 of 6
(1554 views)
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1991 Gmc four wheel drive doesn't kick in Electrical?
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I have a 1991 Gmc Four wheel drive
5.7 Auto light 3/4 ton
loads of miles
When I shift into four wheel drive there is no response from the hubs. Are these hubs electrical or vacumm? It seems to engage at the transfer case but does not engage the hubs?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 9, 2008, 6:08 AM
Post #2 of 6
(1550 views)
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Re: 1991 Gmc four wheel drive doesn't kick in Electrical?
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Look right at the transfer case. I think it uses an electric actuator to engage front hubs,
T
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Double J
Veteran
/ Moderator
Jul 9, 2008, 10:24 AM
Post #3 of 6
(1547 views)
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Re: 1991 Gmc four wheel drive doesn't kick in Electrical?
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OPERATION
When the ignition switch is in RUN and the four wheel drive control lever is engaged, the transfer case switch closes and battery voltage is applied across the front axle actuator The front axle actuator energizes and the four wheel drive gears are meshed. This meshing action of the four wheel drive gears closes the front axle switch, and battery voltage is applied through the WHT (156) wire across the four wheel drive indicator lighting the bulb. Battery voltage is also applied through the front axle switch contacts and PPL (420) wires to the rear wheel antilock brake module. This will keep the antilock braking system disabled in 4WD mode. The in-line resistor (auto trans only) prevents the transmission converter clutch solenoid from engaging when the front axle switch is closed. A transfer case relay is used on one-ton vehicles equipped with dual wheels and four wheel drive. This relay is energized when the vehicle is in 4WD mode. From the transfer case relay voltage is supplied to the transfer case synchronizer.
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greg555
New User
Jul 26, 2008, 5:08 PM
Post #4 of 6
(1524 views)
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Re: 1991 Gmc four wheel drive doesn't kick in Electrical?
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Thank you for your help 
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greg555
New User
Jul 26, 2008, 5:09 PM
Post #5 of 6
(1524 views)
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Re: 1991 Gmc four wheel drive doesn't kick in Electrical?
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Thank you for your help
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repairdad
User
Jan 15, 2011, 2:06 PM
Post #6 of 6
(1272 views)
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Re: 1991 Gmc four wheel drive doesn't kick in Electrical?
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Good Day
My dad's 1993 Suburban is with a new soliniod recently and now
will not engage when it is cold . So reading your previous posts,
thank you , we will pursue a possible stickafacktion due to under coating
and temperature on a linkage if we find an external one. Then get out the
voltmeter.
Repairdad Now graduated from working on my son's clunkers to my dads.
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