# front diff actuator wiring



## mcwlandscaping

4wd is screwed up and has been screwed up in my 97 for awhile. Someone messed with the wiring at one time and GM wants WAY too much money for a new harness. I have one of each the new style and old style front actuator kicking around and was wondering how each works when wired up.

The old style (thermal) has two wires coming out of it. Do i just apply 12VDC to one and ground the other to make it work? Does it need constant power to stay extended?

The new style has four pins (i think!). Does anyone have a diagram of what each pin does? I don't want to experiment and fry the thing! lol

Thanks for any insight!


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## 2COR517

mcwlandscaping;1087086 said:


> 4wd is screwed up and has been screwed up in my 97 for awhile. Someone messed with the wiring at one time and GM wants WAY too much money for a new harness. I have one of each the new style and old style front actuator kicking around and was wondering how each works when wired up.
> 
> The old style (thermal) has two wires coming out of it. Do i just apply 12VDC to one and ground the other to make it work?
> *
> Yes*
> 
> Does it need constant power to stay extended?
> *
> Yes*
> 
> The new style has four pins (i think!). Does anyone have a diagram of what each pin does? I don't want to experiment and fry the thing! lol
> 
> Thanks for any insight!


Have you considered a Posi-Lok?


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## B&B

I recall you working with this a long time ago Mike. First you should determine what was done to the harness, how butchered it is (where and how) and also if the switch at the T-case is still operational. Then go from there. 

1) Does the truck have a single four pin, or two separate two pin connectors at the actuator plug?

2) Do you have a pigtail for the four pin electric actuator to build from if you decide to use it?





The Dog Napper covered your other questions nicely. Simple, but nicely.


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## mcwlandscaping

B&B;1087244 said:


> I recall you working with this a long time ago Mike. First you should determine what was done to the harness, how butchered it is (where and how) and also if the switch at the T-case is still operational. Then go from there.
> 
> 1) Does the truck have a single four pin, or two separate two pin connectors at the actuator plug?
> 
> 2) Do you have a pigtail for the four pin electric actuator to build from if you decide to use it?
> 
> The Dog Napper covered your other questions nicely. Simple, but nicely.


Yea, i thought i had the issue covered but spent all of last winter engaging the front diff via a spacer i had to take in and out manually everytime i wanted to take the truck in and out of four wheel drive! NOT DOING THAT AGAIN!!! lol

I do have the four pin pigtail to use if need be and that's why i was asking about it. I know that the new style actuators are a hell of a lot better than the old. My truck is/was initially wired for the new style but before i knew what i was sort of doing with vehicles, the front half of the harness stopped working and my mechanic at the time couldn't figure out why. He made the old style actuator work with what i assumed was just a switch in the cab for the actuator and the existing button for the T-case. If i can't get the new style to work in any way then I'll just redo this method....just a lot cleaner! The new style would be ideal though.

By switch at the T-case, do you mean the part that sends signal to the front actuator or is the T-case itself functional off of the regular 4*4 switch? The T-Case operates off of the stock switch


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## B&B

Yes I was referring to the switch on the T-case that sends the command forward to operate the axle actuator. 

Since you have the pigtail for the new style actuator you could wire it separately with a manual toggle on the dash if you wanted it that way (allows you to pre-engage the actuator and leave it engaged, similar to locking the hubs for an entire snow event on the older SFA trucks) but I'd rather see you tie it into the original harness so it will engage/disengage via the T-case first....and then add the manual override toggle if you wish.

Need to go over the old harness first to see what needs addressed or repaired before even thinking of making any changes. Then dig into the wiring from there.

Your trucks push button right Mike? They're a little more effort to work with but not overly complicated. Figuring out what's been chopped up and why will take more brain effort than fixing it most likely.


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## mcwlandscaping

yes, it is push button. I have no idea where on the t-case the wires come in/out and go to so if there is some guide to where i need to look and where to start playing with a test light that would be most helpful! 

Just out of curiosity, why did GM switch to the newer style actuators? Just a better design or are the front diffs different yielding the change in actuators?


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## B&B

The change was due to needing a faster engagement from the actuator. If you've run the older thermo style one for any length of time you know they're not the fastest thing, especially when the axle and actuator is packed with snow or it's very cold out. Some would take several minutes to warm up enough to engage the axle. The newer style with the electric driven motors are much faster....almost instant. Thus finally giving owners the Insta-Trac GM was marketing for years prior. Expect now it actuality was instant as it should've been from the beginning.

Here's a pic showing the T-case switch location. Start there and examine the harness closely looking for anything added or hacked into. Same with the harness as it snakes up to the front diff. Somewhere you're going to discover something. Also check how many wires are on the T-case switch and their colors (likely be a brn, Lt blu and or Dk Blu) and let me know for sure. Same up at the axle actuator as there's a couple different systems for '96-'97-'98 as the OBS was changed over.


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## mcwlandscaping

Went through the wiring last night and its a mess. There are 3 wires coming out of the T-case plug, one is broken and rotted, and one of the other two has a scotch block type of add-a-circuit fitting on it (nothing coming out of it) but I have no idea what someone was thinking there. On the diff side the plug has 5 wires coming out of it but doesn't have long enough wires to splice into as they were cut by that previous garage I mentioned and the other wires look kinda screwed up as well. Three of the five wires are cut short, the other two are still connected to the plug. I can get another plug if need be but it looked like I could take the pins out of the current one and replace. I have some pics of the mess if that would help but its pretty straight forward, just a mess.

What's the best course of action??


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## B&B

Yes I didn't figure it would be too pretty, I remember the issues you had with it a couple seasons ago.

Testing and repairing at the T-case is no problem but at the diff appears will take a little more work. If you can at least see the colors on the truck side of what's left of them (for identification if nothing else) we can get that fixed up too if you're willing to replace or repair/reuse the plug with fresh pins. Could alway use a different (easier to source) connector plug entirely too so you do have some options there.


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## mcwlandscaping

Sounds good! I just need to get a friend who can see colors better than I in there and I'll report back! Last night I removed the "fix" that the garage installed a few years ago...what a joke!


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## B&B

Sounds good Mike. Get the colors at the T-case switch, at the original truck side axle connector and also the pigtail you have for the new style actuator and we'll go from there. Not really a tough job once you remove all the mess from the last "fix" and start fresh.


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## Willie56

B&B said:


> Sounds good Mike. Get the colors at the T-case switch, at the original truck side axle connector and also the pigtail you have for the new style actuator and we'll go from there. Not really a tough job once you remove all the mess from the last "fix" and start fresh.


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## Willie56

Hey guys,
I just posted a similar problem. 2000 GMC with NO HARNESS at all and have no idea how to start to get my 4WD working....
How how does a single toggle switch work if you have four wheel low four wheel high and auto? How does that work?


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## Willie56

Willie56 said:


> Hey guys,
> I just posted a similar problem. 2000 GMC with NO HARNESS at all and have no idea how to start to get my 4WD working....
> How how does a single toggle switch work if you have four wheel low four wheel high and auto? How does that work?


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## Willie56

Thanks....I have no switches inside of the truck either… So can I use toggle switch for transfer case and toggle switch for differential?


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## koskieistheman

I have a 4wd issue, I'm not that articulate but ill do my best to describe the problem, I think it closely resembles the first posters problem. I have a 1998 k1500 1/2 ton pickup with pust button 4wd, and an electric actuator, 4 prong. This spring I swapped out the front differential with one out of a 1992 blazer. It installed perfectly except for one small problem, the actuator connections didn't line up. I was able to install the newer actuator and assumed all was well. Turns out the newer actuator was crushed in half. So now I'm left with with older thermal actuator but with all the newer wiring. I know the older units had a separate wire for the selection but all I really care about is having 4wd, 4lo would be an after thought. My question now, is there a way to make what I have work for me? Using the newer connector with the older actuator? Thank you


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## [email protected]

koskieistheman said:


> I have a 4wd issue, I'm not that articulate but ill do my best to describe the problem, I think it closely resembles the first posters problem. I have a 1998 k1500 1/2 ton pickup with pust button 4wd, and an electric actuator, 4 prong. This spring I swapped out the front differential with one out of a 1992 blazer. It installed perfectly except for one small problem, the actuator connections didn't line up. I was able to install the newer actuator and assumed all was well. Turns out the newer actuator was crushed in half. So now I'm left with with older thermal actuator but with all the newer wiring. I know the older units had a separate wire for the selection but all I really care about is having 4wd, 4lo would be an after thought. My question now, is there a way to make what I have work for me? Using the newer connector with the older actuator? Thank you


did you find a way to fix this i have the thermal diff and the electric 4 pin conector


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## koskieistheman

[email protected] said:


> did you find a way to fix this i have the thermal diff and the electric 4 pin conector


I have not, I've heard the 96 through 98 electric actuator is shorter than the older thermal ones. So possibly putting something I the axle tube like a shim might work? Don't take my word for it though, im not willing to waste $65 on a new actuator to test the theory


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## [email protected]

koskieistheman said:


> I have not, I've heard the 96 through 98 electric actuator is shorter than the older thermal ones. So possibly putting something I the axle tube like a shim might work? Don't take my word for it though, im not willing to waste $65 on a new actuator to test the theory


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## [email protected]

I'm playing with the wires in mine I know you have to have the 2 wires at the top of the diff wired in cause it sends a signal to the pcm what 4 color wires do you have


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## Yendor

Did you get your 4x4 to work? I am having problems also.I bought a 1995 suburban heavy half (8hole)6.5 tb and guy I got it from said he put in a different transfer case he did but the wiring harness on truck is 3 pin at transfer case and it has a 2pin switch what to do about this


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