04 Trailblazer 4WD System with a whining noise

Wrathchild · February 1, 2015

Hello all. Just discovered the site, and I'm quite impressed with it. Decided to join the fun

So, my 04 Trailblazer has been dealing with 4WD issues since Thanksgiving. Let me run down what happens and what I've done so far:

Last year in Michigan, we had a brutal winter. Worst in 30 some years. I used my 4WD often to drive from Grand Rapids to Holland on the back roads. (i avoid the highway like a plague with snow and ice) This year I had tried to switch my dial over to 4W high to check the system, and it had problems engaging and had my now infamous "whine" that occurs when I am between 10-40 MPH. Gets louder with higher speeds. When I idle at a stop sign, it sounds like my truck is running loud.

So, I first asked my friend who had done work for me to the truck, and he thought 1 possiblity was the Transfer Case motor wasn't shifting it for me. So I replaced the TC motor, and changed the fluid with the GM AutoTrac II fluid that goes in it. I can now shift quickly into 4WD, but the whine is still there.

Next thing I did was change the fluid in my front diff. Noise is still there.

What are some of the other things I should check?

gmtech4 · February 1, 2015

Hello all. Just discovered the site, and I'm quite impressed with it. Decided to join the fun

So, my 04 Trailblazer has been dealing with 4WD issues since Thanksgiving. Let me run down what happens and what I've done so far:

Last year in Michigan, we had a brutal winter. Worst in 30 some years. I used my 4WD often to drive from Grand Rapids to Holland on the back roads. (i avoid the highway like a plague with snow and ice) This year I had tried to switch my dial over to 4W high to check the system, and it had problems engaging and had my now infamous "whine" that occurs when I am between 10-40 MPH. Gets louder with higher speeds. When I idle at a stop sign, it sounds like my truck is running loud.

So, I first asked my friend who had done work for me to the truck, and he thought 1 possiblity was the Transfer Case motor wasn't shifting it for me. So I replaced the TC motor, and changed the fluid with the GM AutoTrac II fluid that goes in it. I can now shift quickly into 4WD, but the whine is still there.

Next thing I did was change the fluid in my front diff. Noise is still there.

What are some of the other things I should check?

Chassis ears ( on frt diff and t case ) , check oil for material , shop time ,

LET US KNOW ., no one does

02suburbanZ71 · February 3, 2015

Sounds like the tcase might be bad [emoji45]. What rob said.

Wrathchild · February 4, 2015

I'm hoping to have my fiancee help with switching between 2W and 4W this weekend while I listen to it from underneath. We work opposite shifts.

Far as the oil/fluids go, I didn't notice any metal shavings or any other material in it when I drained them both.

Shop time, I've never brought my truck into an actual shop for any kind of diagnosis. I've had my friend help me with any mechanical issues I couldn't tackle. Lately, he's been working a crazy schedule. Haven't had time to meet up. Would I be better off just biting the bullet and paying for a complete lookover at a garage after informing them of the problem?

gmtech4 · February 4, 2015

I'm hoping to have my fiancee help with switching between 2W and 4W this weekend while I listen to it from underneath. We work opposite shifts.

Far as the oil/fluids go, I didn't notice any metal shavings or any other material in it when I drained them both.

Shop time, I've never brought my truck into an actual shop for any kind of diagnosis. I've had my friend help me with any mechanical issues I couldn't tackle. Lately, he's been working a crazy schedule. Haven't had time to meet up. Would I be better off just biting the bullet and paying for a complete lookover at a garage after informing them of the problem?

Yes