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Discussion Starter #1
I'm new to the forum and need help. I've recently gotten a 2002 Trailblazer EXT LT from my parents to use as a work truck so I don't use my car to get in and out of jobsites that often don't have roads or even gravel.

I tried using the A4WD the other day to get across some pretty greased up mud and once I hit pavement the rear tires started dragging behind as I was going straight. I've tried replacing the transfer case fluid and rear differential fluid in hopes that would solve the issue but the issue is still there although not as bad as before. I don't hear any loud grinding or sounds that would be out of the ordinary and everything seems to be plugged in and in working order so I have no idea whats going on or how to get it to work properly.

2WD works just fine and I've notice that when at a standstill with A4WD on, the car won't move after a few feet as if I have the breaks applied. I even put the truck in neutral while driving down my street at less than 20 and the car came to stop.

Any help or guidance would be really appreciated. I don't want to replace anything major yet if I don't have to.
 

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2004 chevy trailblazer_ls_ext
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Welcome to the forums!
First thing I would like to recommend is not to use the A4WD function. This shifts the vehicle in and out of 4WD repeatedly, and it's not very good for the drivetrain parts. This was NOT one of GM's better ideas! Put it in 4HI or 4LO when going off road, then back in 2HI once you hit pavement. Your drivetrain (and bank account) will thank you for it. To put it in 4LO, you first have to shift the transmission into neutral, then engage 4LO. I've read some people say it's good to put it in 4HI before putting it in 4LO, while the tranny is in neutral. Another thing not to use is the lift glass feature. The rear window is bonded (glued) to the hinges, and the stress of fighting the lift cylinders will eventually de-bond the glass, and I have read that it is around $1,000 to have the window re-bonded to the hinges. Lift the entire lift-gate instead.
As for the wheel issue, it sort of sounds like either the transfer case motor or the 4WD actuator (on the front passenger side axle) isn't working right. The 4WD isn't releasing, and you don't notice it due to the lack of traction off of the pavement. My first guess would be a transfer case issue.
Does it do it in 4HI or 4LO, or only when the A4WD function is active?
 

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2004 chevy trailblazer_ls_ext
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OK, if it does it in 4WD but not 2WD, I think we can rule out a rear differential issue. Did your parents buy this TB new? Did they ever run it in 4WD? I'm asking because we recently had a poster with an issue similar to this, and it turned out that someone had changed the gears in one differential, but not both. In 2WD it was fine, but it would lock up in 4WD. Not saying that this is the issue, but if your parents didn't buy it new, and never had it in 4WD, it's possible.

(Edited my original post to specify transfer case motor)
 

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No they got it from a small dealership and they tried once and it did the same thing to them so they kept it in 2HI all the time so I think that may be it then unless I'm missing anything.

Is there anyway to see what the gearing should be from the factory and how to figure out what gearing i currently have?
 

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2004 gmc envoy_slt
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First thing to check, are the tires all the same size? Size does matter in 4WD, if either front or back tires are rotating at different speeds, that will cause issues.
 

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This was recently discussed here. Do this test. Put the car in 4Hi, Jack up one side only, front and rear. Leave the other side on the ground. Mark both wheels at the top, I used tape. Rotate the wheel around 4 or 5 times. The marks must still be at the same spots and the number of revolutions must match or someone has changed the front or rear differential and mismatched the gear ratios. If there is a mismatch I have more simple tests to determime what are the existing ratios.

 

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Discussion Starter #9
This was recently discussed here. Do this test. Put the car in 4Hi, Jack up one side only, front and rear. Leave the other side on the ground. Mark both wheels at the top, I used tape. Rotate the wheel around 4 or 5 times. The marks must still be at the same spots and the number of revolutions must match or someone has changed the front or rear differential and mismatched the gear ratios. If there is a mismatch I have more simple tests to determime what are the existing ratios.

I will for sure try this tomorrow, thanks for linking the video!
 
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