Issue with 4x4

[Jomar]

My Silverado is having issues with the 4x4. It does Engage but it struggles. When I set the 4h it kinds of drags like something is holding it back and it makes a weird sound coming from the front end. If I set it to 4l it really doesn’t want to move. I have to give it a nice amount of gas for it to go but is feels like something is holding the truck from moving. I’m looking for ideas to pin point the issue. Thank you 

[richard wysong]

hows the oil in the front differential? ujoints in front drive shaft ok? manual shift transfer case or electric? if manual jack up the front end, start it up, put it in 4high, shut it off and shift the transfer case back to 2wd and see if everything turns free. USE JACKSTANDS !!!. if electric you will have to jack the back up too and leave the tc in 4wd but put the trans in neutral. any chance some one has changed a diff or ring and pinion and they are different ratios?

[Jomar]

I change the oil in the front differential yesterday. It was milky and gray looking. I did jacked up the truck up this morning and I had set it to 4l and had the wheels spinning and the right front tire struggles to spin. The front wheel more so then the rear. The left wheels spin freely. I have own the truck for the last 2 years and I haven’t had any issues until now. Last time I used 4x4 was about 4 months and it was working fine. U joints look fine. Btw is an 08 Silverado Ltz  vortecmax.

[richard wysong]

thats probably just normal differential function. with out it running do they have equal resistance? all 4 tires the same size and brand?;

[Jomar]

I didn’t try spinning them with the truck off. I can try that on Thursday. The tires are all the same. The front right tire struggling to spin and looking like is getting stuck and then free and stuck again normal? Almost like it has some kind of friction for a short time? And is only happening to the right front wheel.  The both tires on the left side were spinning at a constant speed. I just wanted to clarify.

[richard wysong]

normal action of the spider gears in the diff. unless it's limited slip, if you try to stop the left the right will go faster in an open diff. they don't usually put limited slip or lockers in the front as it won't steer in the slippery stuff