Clunk or bang after 4WD Engaged

[TowingMaster]

Hello,
I have 2005 2500 duramax with 40k miles on it. When I push the 4WD button it makes normal clicking sound that it has made since day 1 and seems to engage normally. When I got to accelerate or put load on it after pushing button I get a load clunk or bang from front end as if it was not completely engaged. It does not make the noise again after the loud bang or clunk. I did a search and did not find anything that sounded similar. Anyone seen this before and what was the fix?
Thanks.

[Mark Rinker]

That clunk are the hubs engaging. It will go smoother if you stay out of the throttle and coast while this is taking place.

If stationary, shift the truck into R, back up a few feet, then D, and drive forward slowly.

If on the fly, decelerate while engaging. Wait for the 'clunk' of the hubs engaging BEFORE applying any throttle.

Remember there are two things happening - the xfer case engaging, AND the hubs engaging.

[TowingMaster]

Thanks for reply. I always engage it stopped or if on the fly I decelerate. It has nothing to do with how I am engaging it as I have done it the same way since truck is new and just started having problem. I would guess it has something to do with the hub engagement. Is there any known issues with this and what would I check for?

[Mark Rinker]

I follow you, and come to think of it, they get noisier and more likely to do that delayed CLUNK at engagement as they get older and looser.

Never had one break yet in the 4WD department, and we run the snot out of them in the winter plowing snow.

One transfer case that was run dry in the off season. That's it for 4WD related issues.

[More Power]

Never had one break yet in the 4WD department, and we run the snot out of them in the winter plowing snow.

I twisted off a stub shaft in the front differential once (during a photo session) in my K1500 Duramax conversion (http://www.thedieselpage.com/features/project2-16.htm). I selected 4wd using the pushbutton with the trans in neutral, then drive/reverse to help it engage - I thought it was.

http://www.thedieselpageforums.com/photopost/data/500/project2-2101.jpg

This is the "Front Drive Axle Clutch Shaft" - or rather what remains of the original. The front axle did not engage till after both rear tires had begun to spin. The sudden engagement resulted in twisting apart the stub shaft that connects the front differential to the passenger side axle. Aside from replacing the shaft and related bearings, there was no other damage done to the front axle assembly. The lesson learned here is to always ensure that the front axle has fully engaged before expecting it to take the power. Was an expensive photo....