The carrier is what is in your diff.

Why would you want or need to grab the driveshaft? It is spinning, the carrier is spinning, the axels spin up to the hubs. When hubs are engaged, they spin the front wheels.

The t-case functions in two speeds, HIGH speed and LOW speed.

Go to youtube and view the process explained countless times, even BorgWarner puts out videos on the subject.

 

Alright, where and what i'm trying to get at on this one, is why my front axles are turning when i'm in 2hi and the hubs are disconnected.

 

Because they are splash lubricated, they need rotation to stay lubed. It also leaves but one function (hub engagement) to happen before full 4WD.

What is the issue with the front spinning anyway?

 

It was mainly due to me thinking that in 2hi, i would not be driving the front driveshaft, and the hub disconnects would mean i wouldn't be 'pushing' the front axles either. But watching a camera of the axles when i'm in 2hi, shows the front axles moving at the speed of the vehicle, and i've confirmed the hubs are disconnected.

I'm chasing all of this because of a kind of grating/scraping noise (metal on metal, not a clicking or grinding noise) that comes on about 15mph and up that comes from the front end and can almost be felt through the steering wheel and floor - only very slightly though.

 

Well, the front end does indeed rotate with the t-case in 2. The grinding will be hard to track down, but I'd bet it is in a u-joint or similar somewhere. Just a hunch.

 

Thanks, that answers that part of my question. The scraping noise doesn't change with steering angle or drive mode.

Whilst you're here being very kind answering my questions, can i assume that selecting 4hi (or low) that i will still get properly locked front and rear axles which will bind if i try and steer on dry pavement?

 

Yes, the 4H or 4L will engage the front end full-time. The 4A will only when the truck feels a slip.

 

Ok, thank you, i need to try and troubleshoot that then, as i could turn fairly sharply at low speed in 4hi, without any noticeable binding I don't know what your knowledge or experience is with these cases, but i'm impressed and thankful for your help on this one. I don't know what would/could be at fault (if anything) in the tcase if i don't get binding when turning on dry pavement in 4hi.

 

The front diff allows the wheels to spin at different rates to prevent the binding. A locked front end would bind at low speed and 4WD.

 

I thought true 4x4 locked front and rear axle speeds, meaning you can't/shouldn't run 4hi on dry pavement as it will cause binding when you're turning?