Motor trans transfer case swap

I think the issue we are going to have is if the new transfer case is a 2-speed automatic or a manual?

I am attaching the wiring diagrams below for each of these. The first 2 are of your GMC.

The next two are the 2-speed auto.

The last is the 2-speed manual transfer case.

I understand that your truck may be set up for an auto shift transfer case as I think all the GMC trucks had the 2-speed auto but the truck that you got this transfer case of could have the auto or manual.

If you have the auto transfer case, then the wiring is slightly different, but you should be able to match up your wiring to try and get this operating.

Here is a guide that will help with any wire testing that you may need to do once you complete this repair:

https://www.2carpros.com/articles/how-to-check-wiring

Please run through these diagrams and let me know if you have other questions. Thanks

Okay. I am attaching the connector views of the actuator on the case which should help with this.

First attachment is the 2004 Chevrolet. The next two are for the GMC. Just looking at this, the issue you are going to have is the GMC runs off an 8-volt system and the Chevrolet has a 5-volt.

I am not sure there is a way to change this so I would see if the actuator from the old transfer case fits the Chevrolet so that you can keep the control side of it the same.

If this were anything other, than a Chevyrolet/GMC I would say it most likely had not been done but it seems like everything has been tried on these trucks, so I am sure someone has tried this.

The unfortunate thing, I am not sure how it would work since the 5-volt reference on the Chevy truck is supplied for a specific reason. It sends 5 volts there and then based on the return signal which is going to be between 0-5 volts, it tells the control module what position it is in.

Basically, if it sends 2 volts back to then that means it is in one position, if it sends 4 volts back then it is in a different position.

So even if you use resistors and get the 8 volts down to 5, the signals returns are most likely not going to match up between the 8- and 5-volts systems.

Basically, if you have a control module that is expecting the 8-volt system, and you knock it down to 5-volt then it will not recognize it. So, you would need to change the control module as well but that is going to introduce communication issues with the rest of the truck.

I think this is one of those cans full of worms.

If you are willing to try it then we can try and walk through it, but I just want, you to have that understanding prior.

It may be worth while trying to find a conversion kit. I did some searches and didn't find anything. I will put some feelers out to some Chevrolet guys I know and see if they know anything.

Funny. We should be neighbors. I will not touch body and paint so we could work on each other's stuff.

Yes. A transfer case would fix it but I have not looked at the actuator on these vehicles in a while, but it may be worth trying to just change the encoder gear. You will have to remove the snap ring, but it should come out.

Then if you can put the GMC encoder with the Chevy gear in it so that it splines into the transfer case but also plugs in and operates with the GMC commands, you should be able to get it working.

As for programming it to operate the Chevrolet set up, that will not work either. Unfortunately, you will not be able to flash the module with the other software so you would have to replace the control module but that again creates communication issues with the rest of the existing modules.

Unfortunately, these two trucks use practically identical parts, but they operate off different control systems. So, it is like they speak different languages so you can change all the parts, but they don't know how to talk to each other.

Okay. That is what I am not sure about. However, if you can remove the gear/splines and swap them then that will solve the issue. Basically, you can use the GMC actuator with the Chevrolet splines so that it connects to the Chevrolet transfer case.

I am not saying that this is possible, but it is the only chance I see at making this work. At least it is the only one I can think of.