T-case wiring

[b454rat]

So on my Yukon, it had the Autocrap and swapped it out for a manual 241. Easy enough, 100% bolt it. Hardest part was getting 246 out, it's lil more portly than the 241, but it's out. Since it's manual, pull the magic lever and the front shaft spins, but front doesn't engage. Looking over wiring, looks like the brown wire is supposed to be hot going to the actuator. I traced it from the actuator, to the range switch on the t-case, but no clue where it goes from there. Since it's supposed to have power, and when 4wd is engaged, the grey/black wire grounds out, and makes the actuator do whatever its supposed to do. Trying to get this going, so could I just put the brown wire on a switch? Or where does it go so I could check on the other end?

 

[KansasOBS]

The brown wire is just supposed to be fused power from the cab to the actuator. The selector on the transfer case receives no power, everything is triggered by a ground.

I'm guessing since yours had the autocrap, that they sent the power from the cab to the Tcase in a different manner, the brown wire probably just chained off of it. My manual Tcase OBS truck just had a brown power coming out at the firewall plug from the 4x4 fuse inside.

The actuator needs power, a normal ground, and a ground to trigger it. The selector needs a ground, and then feeds this back to the actuator, and then another ground to the PCM when in 4low. The actuator is responsible for the indicator/lights, whatever.

You could just wire the actuator trigger ground to a switch, but if youre running a 4L80, then the computer will also need to know when its in 4low, which comes from the selector normally. LT1swap has the pinouts for the older PCM's, but I don't know them offhand. Did an LS swap on mine, and used the wiring from the NBS donor truck, as it had a manual Tcase also.

Here is a video on the actuator, and a wiring diagram that might help a little. I forget what goes where on the selector at the Tcase, but its too cold and dark out right now to go take a peek.

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[b454rat]

I watched LT Tolmans swap on an OBS suburban. But one part of the swap where he didn’t go into detail. He didnt say what to do with the original wiring, only that he ran a wire to the actuator and one to the ECM for low range. But after looking online, staring at the wiring for a bit, came to the conclusion that the brown wire is hot when key is on. But still trying to figure out why I dont have power to that brown wire. I took the 4wd fuse out, as LT did as well, but somehow he has juice to it n I don’t….

 

[GoToGuy]

Have you traced and checked from Inst. Fuse panel downline. The diagram shows more than one connector. It maybe time to hand trace check and ohm the circuit.

 

[KansasOBS]

Kinda funny, I almost linked you an LT video he has on the selector, but don't like to promote his stuff really.

I had ditched all of my wiring originally, and was going to just put in a posi-lok, but then just as of a couple days ago knew I may need my 4x4 working, so grabbed the wiring from my NBS donor. Also thought about just using a switch, though in the most simplified manner, it would have required one for the 4low, and the actuator. Just kinda recently been through all of this myself, though all my stuff was manual from the start. The setup isn't too bad once you get figured out what you need.

My 4wd fuse is powering the brown wire, and yeah youre right about it being keyed power. I guess do as GoToGuy said, or just stick a fuse in and check.

 

[b454rat]

I’ll try that. I’d like to get it working for now, have too much other crap going on to start another project. If checking fuses n tracing wires don’t work I’ll run a hot wire to it with key on n check that, maybe just leave it like that lol….

 

[xx94Z71xx]

hey guys... im having the same issue here. my 4x4 fuse keeps popping but its only when im driving and give it some gas!. i replaced the actuator with a known good one and the fuse still pops. im having a little trouble understanding the 3 wire transfer case switch. how would i go about bypassing this? i understand 1(brown?) wire is 12v switched coming from 4x4 fuse. 1 wire goes to the PCM. what do i do with the other wire? is this switched ground? they say with a 2 wire switch you can just bypass it. how would i got about this with the 3 wire? any clarification would be great. can a bad transfer case switch cause a popped fuse?

 

[b454rat]

I’d try that first. On the t-case one of the wires is a ground. One goes to ECM for 4 low n other goes to actuator.

 

[xx94Z71xx]

thought id come back and say i ended up just using an add-a-circuit fuse, and running a toggle switch and wire down to the actuator. works like a charm. and if im correct the 4Lo will still work properly because i left the trans case switch in place and connected, because PCM looks for ground in 4lo. so i just left the fuse out of the 4x4 circuit.

the light still works as well. i went 12v down to one line on the actuator, and spliced into the light blue wire running to the solenoid switch. switch works by completing ground. only downfall is when u kill the switch the light immediatly goes out. so after a few mins of it being off i just blip the switch andd make sure light stays off. takes a bit for the actuator to warm up. hope this helps someone. was easier than i thought