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SlimPickinz

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Hope this is the right spot, I have a 96 k2500 6.5TD, the 4x4 won’t “lock in” to 4hi, just blinks, I used to have to go from drive to neutral and back to get it to work but now it blinks, if I hit 4lo, the 4 hi light goes solid and the 4lo light blinks but the front tires spin even though it’s blinking. Just replaced the switch on the console. I had the actuator out and put power to it and the end came out about an inch but not fast but no exactly slow. Is it the actuator or encoder motor? I plow snow so i really need the help. Also got a upull encoder motor and actuator this time last year
 

RichLo

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Does the transfer case go into low when its blinking? if it does, you can basically bypass the diff actuator temporarily or semi-permanently by finding a socket with a very close outside diameter as the hole that the actuator goes into and pile up some washers inside the socket... then put that whole assemby in and re-install the actuator. Add/remove washers as needed to engage the teeth in the diff but dont go as far as to crush the actuator.

Probably not the best advice but it'll get you snow plowing. Otherwise you can buy a new actuator and see if that helps.
 

GoToGuy

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You can also buy a " fixed position" adapter. Substitute the actuator for a always engaged front axle fixture. One of the four X four shops were advertising front axle goodies, abd I read about it. Good luck.
You might look in service manual about the electric engagement.
 

SlimPickinz

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Does the transfer case go into low when its blinking? if it does, you can basically bypass the diff actuator temporarily or semi-permanently by finding a socket with a very close outside diameter as the hole that the actuator goes into and pile up some washers inside the socket... then put that whole assemby in and re-install the actuator. Add/remove washers as needed to engage the teeth in the diff but dont go as far as to crush the actuator.

Probably not the best advice but it'll get you snow plowing. Otherwise you can buy a new actuator and see if that helps.
So it seems like if I’m in neutral, and I hit 4lo I can hear it clunk, and the light blinks, but 4lo works, if I hit 4hi, nothing, but if I hit 4hi then 4lo then hit 4hi again it clunks and 4hi works but the light still blinks, how far should the actuator come out when given power? And should it be fast? At this point I’m pretty sure it’s the encoder motor
 

SlimPickinz

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When sitting stopped with the key on but not running, when you press the 4 hi button can you hear the electric motor on the transfer case?
If I hit 4lo it clunks, then if I hit 4hi it clunks, but the light blinks constantly in both ranges, if I just hit 4hi it blinks and I only hear a click
 

mr_josh

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Will it go into 4 Hi from 2wd if you are, say, driving slowly on a gravel road? I don't think your problem is the front diff actuator.

J
 

GoToGuy

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I'm not sure, but on the pushbutton 4X4 does the owners manual say to engage 4X at a less than 10 mph (?) As in a moving vehicle. (?)
At work now, my 95 has stick on floor, the 98 Tahoe has pushbutton. Look in it owners manual at home.
 

Nad_Yvalhosert

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To engage 4x4 low, you need to be stopped, parking brake on, transmission in neutral; per the owners manual. If you're not doing that, you're risking damage to the t-case.

If the indicator light is flashing, it's trying to shift, but hasnt finished.

What do you mean:
@SlimPickinz said: "had the actuator out and put power to it and the end came out about an inch" ?

It's supposed to turn in a circle, not extend out of the case. If it does, it's broken.

All GMT400 trucks have shift-on-the-fly 4x4 high. If you're not getting high, there's a problem, either electrical or mechanical.

Try this: jack up the truck on stands,
engine off ignition key on,
tranny in neutral,
remove the encoder motor and,
with a wrench,
shift the t-case through all positions.
Use your hands to spin the front driveshaft. Does the front driveshaft spin the front tires, does it transfer backwards and spin the rear tires?
 
Last edited:

SlimPickinz

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To engage 4x4 low, you need to be stopped, parking brake on, transmission in neutral; per the owners manual. If you're not doing that, you're risking damage to the t-case.

If the indicator light is flashing, it's trying to shift, but hasnt finished.

What do you mean:
@SlimPickinz said: "had the actuator out and put power to it and the end came out about an inch" ?

It's supposed to turn in a circle, not extend out of the case. If it does, it's broken.

All GMT400 trucks have shift-on-the-fly 4x4 high. If you're not getting high, there's a problem, either electrical or mechanical.

Try this: jack up the truck on stands,
engine off ignition key on,
tranny in neutral,
remove the encoder motor and,
with a wrench,
shift the t-case through all positions.
Use your hands to spin the front driveshaft. Does the front driveshaft spin the front tires, does it transfer backwards and spin the rear tires?
I unscrewed the thermal actuator from my front dig, and put power to the unit, it extends out. This is the actuator I have
 

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