What is the max speed that you can engage your 4x4?

I have done it when I’m driving in town (say like 20MPH) and I get a load clunk. I’m not on the throttle usually I’m coasting. Is this chain slap or just the way it is?

I go from 2 to 4 hi @ 80 mph....seamless

and there is no clunk?

No clunk, 35K now, things could change later.

Mine does the clunk sometimes going from 2H to 4H. I'm starting to wonder if it's a sign of pump rub. I had my T-case changed right around 100,000, and its now at 160,000. I think mine is getting worse now that I think about it, just like last time before it went on me. Anyone know if this could be a sign of pump rub coming up. Also, I have the manual transfer case and sometimes it is really hard to pull the lever back into 4H, even with no throttle.

i haven't had any kind of significant clunking at low speeds that i've noticed. Today i went from 2H to 4H at like 60mph with no throttle and had a decent clunk though. i'm about to click over 200k and it's the original t-case.

I believe on the NP261 it actually engages a collar similar to a synchronizer to make the front output spin. On the half tons with the NP246 it just engages a clutch pack so really you can kick it in any time with no noise, no nothing, thats in 4 high only. 4 low is going to make noise regaurdless and it can only be done while stopped or with a very very slow roll. As long as you don't have any torque on the driveline its probably fine to go in and out of 4 high on the run. Whats the little black book in the glove box say?

I've noticed that the "clunk" occurs when the front and rear wheels are spining at two different speeds. For example I've tried to go into 4 hi when i'm on ice/snow; the back tires are just turing from the idle and the front are stopped. When the t-case engages, a clunk occurs. I've done this same thing before (while pressing the brake, to make sure the back wheels are stopped) and the tcase engages noise free. That's the only time i've ever gotten the clunk.

I've got an '04 also, makes the same clunk you have at speed. Dont worry about the noise, GM states driveline clunk into 4HI is normal. 70K miles so far, no problems. Engaged at whatever speed I need it at.

I shift from 2hi to 4hi and back at 60 or more all the time no clunk, but never while rears are slipping. If rears are slipping I let off then shift.

Sounds good!

I guess I will keep abusing it the way I have been!

Thanks Guys

listen the maunel says NOT to engage 4 hi at speeds over 80 kpm or 50 mph most likely because its hard on it. now that being said ...sure u can engage it at 100mph if u want , is it good for it ****** no ,so dont beat on it if u want it to last.

Mine clunks when rolling when it goes into 4x4 but there is no clunk when rolling and put back into 2wd. I make sure to put it into 4x4 when stopped.
Havent had to do a rolling 4x4 engagement yet more than 10 mph.

The Manual says you can shift from two wheel to four wheel drive at any speed, But in cold weather they recommend you be going slow as the front will not engage quickly. I personally have had that happen to me if I engage four wheel high when it is cold the front axle does not engage right away and clunks big time when it does.