4WD grinding

[Timthetruckman]

Hello,

I have a 2001 GMC Sierra 1500. When I put the truck in 4WD there is a grinding noise made when accelerating and decelerating. It also shifts hard. The front wheels also seem to shift when I come to a stop, then when I move forward they seem to shift back. Also makes a lot of noise when I'm turning. Thoughts, ideas, anything will help. Thanks.

[NSFW]

That could be a tonne of things.

I would un-screw the 4wd actuator in the front differential and cycle it while its hanging from its wires (or have a buddy do it in the cab, while your under watching it) and see if its actually actuating. It should have a full throw.

If you put the t-case into auto4wd is the situation the same?

[Timthetruckman]

it has a manual selector on the floor with no auto 4WD. Also, it does go into 4WD and it works, just makes a lot of noise.

[arcasey]

Are you in 4HI or 4LO when you are experiencing these issues? Or does it occur with both?

[Timthetruckman]

4HI.

[arcasey]

Okay, then it sounds like you do have an issue somewhere. No problems when in 2WD?

 

I just went through the process of chasing some 4WD issues myself. One thing you can do, if you have the space and the time, is jack your truck up and put it in 4WD. I would put the transmission in Neutral but you don't have to. Pull the front drive shaft and then spin the differential to see if you hear any grinding noises in the front differential. Try spinning it with the wheels straight and turned to either side. If there is no issue there and you don't have any issues in 2WD, then chances are your issue is the transfer case.

 

Another thing (and I'm only mentioning this because I don't know how experienced you are with 4WD's and GM) is that 4WD is going to inherently increase the noise you hear just from all the extra parts that have "now become part of the drive line." Turning in 4HI and especially 4LO are going to make a lot of noise. With that said can you describe the turning noises a little more in detail?