2015 GMC 3500, 2wd Lo???

burbguy82

burbguy82

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This question is for some of the fellas that have a bit more intimate knowledge of GM drivetrains and their design. This particular one is a 2015 3500 HD. This is regarding a manual shift NP 261

So I have wondered in the past if 2wd lo range could be obtainable through adding a switch to the front diff actuator. As I understand it, the front actuator locks both sides of the diff together. All items spin of course in 2wd, but not under driven power. Front actuator is ground switched?

So the question is: would their be any adverse conditions in running the tcase in 4lo, but not actuating the front diff?

Reason would be, low speed, and tight maneuvering of a heavy trailer, in reverse aswell. My concern is of course, running 4lo 4wd on surfaces where traction is good.

I brought this up off topic on a separate thread, but cannot find it to revive.

I think the ability to run in 2wd lo would be a pretty serious advantage to some.

@clinebarger
@GMBoy

and any others who I am not aware of who might have some intimate technical knowledge on the subject........
 
I'm not skilled enough to answer this question, but I do know many people have made this modification with the 3rd gen Tacomas, and I think it was done just by a modified switch they installed or something like that. Sorry this is so vague, but I can tell you that yes, it's been put into practice out there.

Here's a random link, maybe it can help?

https://www.tacomaworld.com/threads/2lo-modules.708941/
 
If just for a short time, like you describe I don't see an issue, but you increase the possible maximum torque for the rear drive (which otherwise gets split. That could be an issue for continued use (though I fail to see a use case for that)
 
Jetronic said:
If just for a short time, like you describe I don't see an issue, but you increase the possible maximum torque for the rear drive (which otherwise gets split. That could be an issue for continued use (though I fail to see a use case for that)
Click to expand...
So it is your thought that the toque would no longer be split, sending 100% to the rear?
Makes sense.

I was thinking the opposite, kind of. I was thinking that the maximum torque output would not change to the rear, are torque would still be sent to the front, through the driveshaft, but not used.

I wonder if that is why carmakers no longer offer 2 lo, as it was in some models in the past.
 
burbguy82 said:
So it is your thought that the toque would no longer be split, sending 100% to the rear?
Makes sense.

I was thinking the opposite, kind of. I was thinking that the maximum torque output would not change to the rear, are torque would still be sent to the front, through the driveshaft, but not used.

I wonder if that is why carmakers no longer offer 2 lo, as it was in some models in the past.
Click to expand...

If you have a differential between front and rear, the torque would all be sent to the unloaded side (no drive in this case), but if it's locked it all goes to the loaded side. Same deal as you get with a differential between wheels, with one wheel in the air that spins and the other is stationary, unless locked.

Of course, if you had a differential, you could use the 4lo on any surface.
 
Jetronic said:
If you have a differential between front and rear, the torque would all be sent to the unloaded side (no drive in this case), but if it's locked it all goes to the loaded side. Same deal as you get with a differential between wheels, with one wheel in the air that spins and the other is stationary, unless locked.

Of course, if you had a differential, you could use the 4lo on any surface.
Click to expand...
Make sense, and any one who has a locker knows that they break axles. good point. You are still moving the same weight, with more torque, on less axles. Thanks for the input.
 
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