[bb73]

hello,

I have a 2004 trailblazer (28K miles) which periodically groans, shudders and almost dies when in AWD or 4WD-HI, especially when pulling into a parking spot or turning a corner and other times when driving at slow speeds. It's been doing this off and on for about 2 years now and I've taken it to the dealer to check out 3 times. The first time it was an electrical issue with the 4WD switch. After fixing that it was good for about a year before the issue came back. The second time they couldn't find a problem and it never made noise or shuddered for them when they drove it. The third time I made sure to the engine was warm and that it was acting up immediately before bringing it in. Finally they noticed it, but this time said there was nothing wrong. They said it's common for the the AWD and 4WD to groan and shudder when driving on dry pavement. I don't make a habit of leaving the 4WD on when on dry pavement, but sometimes if I'm off-road, then going back to pavement I don't immediately remember to switch back to 2WD. During the winter when there is snow and ice I use the 4WD a lot and have noticed the groaning/shuddering then as well. That's not dry pavement! When I mentioned this they gave me a round about answer regarding the way the gears mesh and blah, blah blah. They basically stepped around it. I should also mention that the "check 4WD" light was coming on every now and then before bringing it in this third time. They said it was some faulty error code and it was re-set and shouldn't come back on again.

I'm no expert, but this issue being normal doesn't seem right. Has anyone else had this problem?

thanks!

 

[GaryL]

Driving on dry pavement in 4wd will cause it to shudder when turning sharp because of the way the gears are set up in the transfer case, but if it is also happening on snow/ice, then it sounds like there is a problem. I would take it back to them before your warranty runs out (if it hasn't already) and insist on them fixing the problem, especially since the 4wd light was on. Make them tell you what the code was.

 

[Cableguy]

A previous disscussion on the same subject. Hope it helps.

http://www.gmtruckclub.com/forum/showthread.php?t=3627

 

[tbplus10]

Try a different dealership. This one sounds like they really dont want to chase the problem. As posted if the light comes back get them to tell you the code. A faulty error code removed is not a repair. Error codes happen for a reason either the 4wd computer has issues because its giving faulty codes or the system has issues.

 

[MrShorty]

As noted, it will groan and "hop" in 4H on dry pavement because the front and rear are locked together.

My '98 use to groan and scuff in 4A as well, but it doesn't anymore. At first I thought it might be normal. I needed to change the t-case fluid, so I put my finger in the fill hole and it came out pink. A little research on line and at the dealership convinced me that someone had erroneously put DexIII in the t-case. The Autotrak t-case needs Autotrak2 (AT2) fluid for the 4A setting to work right. Changed the fluid and the scuffing/groaning in 4A went away.

One of the first things I might do in your situation would be to check the t-case fluid. Make sure it's full, blue, and clean looking.

It woudn't hurt to get them to pursue the computer diagnostics, too.

 

[cayman2k]

I have the same problem with my 2000' Suburban. I replaced the switch unit since it was lighting up incorrectly . Yes, basically when you are in auto 4 or hi 4, I hear noise driving straight and when I am in a parking lot, I even feel it locking up to the point the truck appears to be braking. I am still trying to isolate the problem but if you hear a fix let me know.

FYI, I replaced the front and rear diff with fluids and added additive for the diff...but the center diff I am going to replace the fluids...

I will let you know if I fix it.