2004 yukon When engaging to 4 hi you hear it engage. In neutral to engage in 4hi or 4lo it makes a loud clunk. I have the driveshaft off now. The output to the front axle turns when engaged.

Have you had codes checked ? While connected to a good scanner that will check transfer case switch to show if switch is working, and it could be the switch on the side of the transmission.

Gm makes lots of different trucks with lots of different engines using lots of different transfer cases. How about not keeping all that info a secret

Try shifting the transmission into neutral then pressing 4hi. It should flash and then engage. Shift into drive again and re-try. Anytime shifted from 4hi to 4lo it needs to be shifted into neutral during transition. There is no need for 4lo position, unless you are really stuck off road, in the mud up to the windshield. Do not use 4lo unless you 4WD off road.

Not to engage 4Hi. You only have to shift to neutral with the vehicle not moving to shift to 4lo or from 4lo

Hi, depending on the vehicle, there can be different controls. Standard control, 4hi, use in slippery conditions, never on dry pavement. Just push the button, and it will engage. 4low is for extreme conditons and the transmission must be in neuteral to engage 4lo. If you have auto 4wd button, just press the button in slippery conditions. If you have a denali, it is all wheel drive, and there are no buttons to push. So, depending on the model, there are multiple ways, but pushing the button engages it. Good luck...Goop

You should be able to put in 4x4 while in drive less than 35mph. Mine had a switch to turn to engage or dis-engage.

what causes the 4wd to kick in when you have it in 2wd

your doing it right but your accuater is bad 59.00 auto zone easy install

It is somewhat Normal Depending on how Loud the Clunking is. This is a Common Complaint on the Chevy 4x4's. I have verified this through the Dealerships here in Oklahoma and they all say the Same thing But, I am with you, They should go into 4x4 without that Clunk for as much as we pay for them.

do you have outside locking hubs?