Ok so I had this posted on trailvoy.com and the Rodie told me to bring it here so here I am. My wife has a 2006 gmc envoy with about 80,000 miles on it. A couple of months ago it started to clunk when it was in a4wd. There is no noise at all until you get to about 25mph. You start to hear what sounds like road noise at 25mph to about 32 or 33mph. When you hit 34 or 35mph it clunks. Then the road noise goes away. It clunks again once you get to almost a complete stop. I replaced the transfer case because that was bad. I got one with about 40,000 miles on it. Replacing the tcase fixed the shifting into 4 low problem but the original problem "the clunk" is still there. I changed the front diff fluid and there was no metal in the fluid. The u joints and cv joints and wheel bearings all seem to be ok because there is no slop in any of them. It does NOT make any noise when it's in 2wd. I even took it to The gm dealer here and they are not sure and they don't want to start throwing parts at it if they don't need to be replaced. I need some help with this please because it's going to start snowing in the next couple of days and she is going to want 4wd. Thank you for your help.
Clunking when in a4wd 2006 envoy
- Thread starter Bigpiper1
- Start date
The dealer has a Tech II scan tool that command the transfer case through its various modes. If they're stumped, I'm not sure we can do a whole lot.
But if your wife uses or used A4WD too much, such as ANYTIME it wasn't absolutely called for by conditions of partial ice or snow, it could have done damage internally especially to the clutches. But you say you changed the tcase. What was the 4LO problem? There's an interlock on 4LO to the tranny has to be in neutral before it will shift in or out of LO.
But if your wife uses or used A4WD too much, such as ANYTIME it wasn't absolutely called for by conditions of partial ice or snow, it could have done damage internally especially to the clutches. But you say you changed the tcase. What was the 4LO problem? There's an interlock on 4LO to the tranny has to be in neutral before it will shift in or out of LO.
I took it in to the dealership after I replaced the tcase. I knew the tcase was bad because when you would put it into 4 low going the one to two mph the whole truck would shift to the left and there was a horrible noise that came from the tcase when doing it. I changed the tcase out and that corrected the shifting into low problem. However the noise that started all this is still there. So yes I think you are correct in saying that it has to be from the tcase forward but like I said before the dealership confirmed everything that I thought by telling me that the u joints the cv joints and the bearings all seem to be ok because there is no slop in them. I'm not sure if it makes the noise in 4hi or just a4wd.
I had that same clunk on my tb it almost seemed like the truck wasn't able to engage the front diff but mine was caused by low fluid on the diff. If u r saying that u changed the diff oil and ur u joints and cv joints are good check the shaft from the tcase to the front diff maybe any bushings if any or the system that engages the front drive shafts including the bearings in the front diff! That's my two cents anyways hope it helps!
See i don't know if it would be the bearings cause you would think it would make the "road noise" all the time. the actuater is doing its job ad far as u know because if its in 4hi the 4wd is working.
Bigpiper1 said:
Good point with the road noise but your 4hi can work just fine and as u know the a4wd only kicks in the front wheels when it notices a slip on the rear, now I don't kno if there is a module controlling that or if it's mechanical but that system could be malfunctioning trying to connect and disconnect the fronts causing the clunk. It's worth taking a look at! The only other thing I can think of is damage in the front diff!
The problem with it sensing slippage in the rear tires to engage the front is that there isn't any slippage cause there is no snow or ice or rain to make the rear tires slip to make the tcase think that there is slippage to make the front engage.
It's electrical, controlled by the TCCM, with two motors doing the work. For more reading - Required for offroaders: Offroadtb.com Transfer Case Operation: NVG 226 (NP8)Andrade said:
Couldnt it be the tccm sending wrong information saying there is a slip when there isn't and the realising there isn't and making the fronts engage and disengage? Just a thought...
