Swapping front diff help

[jamesdking]

98 Yukon 4x4 auto. Front diff grinds loudly in 4. Swapped fluid for fun, no change.

Bought a front diff off marketplace. Told him the GT4 RPO code and that it’s 4x4 auto buttons.

Got to looking at it (new to me diff) and it’s got two plugs. One to the actuator itself. And one to the base of it where it connects to the diff. It’s from an unknown gmt400. I thought since he asked the right questions about gearing and auto 4 I would be on the right part.

Mine (the Yukon) has a single plug going to the actuator. 5 slot 4 pins.

I started with the sticky thread but it’s 85 pages!

I understand that something will have to swap. I’m hoping it’s the wires, plug or actuator. Not the axle ends since mine leak and probably killed my diff. Among other leaks.

Any help is appreciated. First two pics are mine. Second two are the new one.

 

[KansasOBS]

The actuator should have the same plug. The diff you got is from an earlier model, that had the thermal actuator originally. The other plug is a switch thats tells when its in 4wd. That was integrated into the servo actuator later on. Can just ignore it.

 

[evilunclegrimace]

The actuator should have the same plug. The diff you got is from an earlier model, that had the thermal actuator originally. The other plug is a switch thats tells when its in 4wd. That was integrated into the servo actuator later on. Can just ignore it.

My '98 still has the engagement switch on it with 2 seperate plugs. '97 and up 1500's had a steel passenger tube on them and the earlier units had aluminum tubes. I have never seen a front diff that did not have the engagement indicator switch.

 

[KansasOBS]

My '98 still has the engagement switch on it with 2 seperate plugs. '97 and up 1500's had a steel passenger tube on them and the earlier units had aluminum tubes. I have never seen a front diff that did not have the engagement indicator switch.

I have a 98 tube without one, that also doesn't take the the extension slug when that's required when converting from thermal. Factory servo actuator. Suppose my fault for assuming it was just for earlier stuff. 3500 truck.

 

[Vikingdude]

The second bit is a switch. In my truck, when the front dif is actuated the switch is tripped and it completes the circuit to the lightbulb in the 4x4 lever housing. I assume its similar with the electronic transfer case models, but maybe not. 97 was supposedly the year a lot of models started switching form the thermal actuator to the electronic motor actuation.

 

[jamesdking]

So then maybe this better asks my question. How do I overcome the differences in wiring layout in the plug.

First pic is of the new to me diff. The other pic with the glove is my Yukons harness.

Do I need to swap the actuators to overcome these differences or rewire my harness?

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[jamesdking]

So I think I can use my new actuator from the dead diff with my current wiring and will need the spacer from the wiring kit to make this work. Anybody ever been able to substitute a common object or know where to source it alone?

 

[evilunclegrimace]

I have a 98 tube without one, that also doesn't take the the extension slug when that's required when converting from thermal. Factory servo actuator. Suppose my fault for assuming it was just for earlier stuff. 3500 truck.

I just figured out the the diff that I thought was a '98 is a'97. So you are correct that the later units don't have the small engagement switch. The axle tubes that dont have the small switch are shorter were the actuator screws in by about 3/4"

 

[Nad_Yvalhosert]

One of those trucks was equipped with a NP243 t-case with the push-button 4x4.
The other one had a NP 246 AUTO-4x4 t-case.

Unscrew and use the front diff actuator that came with the truck.

 

[evilunclegrimace]

One of those trucks was equipped with a NP243 t-case with the push-button 4x4.
The other one had a NP 246 AUTO-4x4 t-case.

Unscrew and use the front diff actuator that came with the truck.

The actuators are the same for the 243 and the 241. The 241 was in the floor shifted T case.