1990 Chevy Silverado 4WD not engaging

Tiny
MB12868
  • MEMBER
  • 1990 CHEVROLET SILVERADO
  • V8
  • 4WD
  • MANUAL
  • 115,000 MILES
1990 K3500 Dually, manual tranny. 4wd on floor.

4wd is not engaging while in 4HI. I can sometimes get it to engage while in 4LO. I was able to get in 4wd yesterday, but felt like it was not fully engaged.

Would this be an actuator problem or a weak one?

12/9/2009 ---
ordered a posi-lok for the truck to truly eliminate the actuator issue.

I also have read this could also be tied to an ABS issue, looking for feedback on this. I will try to pull the ABS fuse to see, need to wait for the blizzard here to pass.
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Tuesday, December 8th, 2009 AT 6:13 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
To me, it sounds like an actuator problem. If the problem was related to other areas, you wouldn't be able to get it in 4lo. Remove the actuator to check and see if it is actually functioning. Also, check power from the switch. I have seen switches that will light a test light, but when placed under a load, the stop working.

Let me know what you find.
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Friday, December 11th, 2009 AT 10:19 AM
Tiny
QUAGMIRE86
  • MEMBER
Also, the shift fork (attaches to actuator) may be worn down enough to cause intermitent engagement or no engagement at all. I had a similar problem to yours on a Blazer. 4wd was ok until I turned the wheels right or left, then it would "Pop" out of 4wd. The problem was a worn shift fork in the front axle. Fairly easy fix, just have to split the front output shaft to get at the shift fork.
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Saturday, December 12th, 2009 AT 10:12 PM
Tiny
MB12868
  • MEMBER
Well, installed the posi-lok. Pretty easy to do.

It didn't fix my issue, but I know for sure that it is not the actuator. The passenger side axle is floating( I can push it in and out a couple inches). Any ideas? I am going to have to drop the front diff, but will have to wait when there is not a blizzard out again today.
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Monday, January 25th, 2010 AT 7:18 PM
Tiny
KMCCHEF
  • MEMBER
I don't know if it is the same on the K3500 one ton, but I had a problem with my 4 wheel drive, and the guy said it was a thing called the Donkey D**k. It might be what you are calling the actuator or not, but when he installed a new one on mine I never had a problem again.
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Friday, February 11th, 2011 AT 2:07 PM
Tiny
MB12868
  • MEMBER
Well, the Axel floating was the issue. The passenger side axle was not attached according to the mechanic (yes, after I had to physically show him as he didn't find any issues). There is a bolt and washers that hold the Axle in and that had broken. It works again and there have not had any issues with this Problem.
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Friday, February 11th, 2011 AT 2:51 PM

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