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04 Trailblazer
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Discussion Starter #1
Good evening, new to the site as of this evening. I've used the search function as best as I can but can't find a duplicate issue. I just bought an 04 TB with 122,000 miles. The car is immaculate and was well maintained. It was owned by the service manager and his wife of my local dealership. Here's my issue, I live at the top of a long steep hill. We got quite a bit of snow today. Before starting up the hill I stopped, and shifted into 4wd. The indicator showed it was engaged and I started up. The the rear tires started spinning....it was not in 4wd. I backed up and tried it again with no luck. I shifted into neutral> 2wd> 4wd hi and placed the TB back into drive. No difference. I then shifted into neutral and 4 lo. No such luck. I backed into the street and went around the block. Shifted into 4 hi about 1/2 a block from the hill and then started up the hill, BOOM 4wd worked like a champ. I made it to the top and promptly turned around and drove back down. Tried it again from a stop shifting from 2wd to 4wd and same issue, no 4wd. Shift from 2wd to 4wd while driving and the 4wd works like a charm. Sorry for the long post but I tried to be as descriptive as possible. This is the first electronic shifted 4wd system I have ever owned, all my previous vehicles have been lever shifted. Is this an issue or is this normal?
Thank you for any and all help!
 

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2002 chevy trailblazer_lt
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912 Posts
These vehicles can be shifted from 2Hi to 4Hi or A4WD at any speed. The only times you must be in transmission neutral for a shift is when shifting either into or out of 4Lo as well as shifting the transfer case into neutral.

For shifts into or out of 4Lo the recommended method is to be in transmission neutral and rolling less than 2 mph.
 

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04 Trailblazer
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7 Posts
Discussion Starter #3
TJ thank you for the reply. I guess my main issue is 4wd only send to engage while the vehicle is moving. My main thought is will it engage if the vehicle becomes stuck in 2wd.
 

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2003 Chevy Trailblazer LT
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220 Posts
How about service 4wd light ? Ive made a few post and never got any resonse to them
 

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2004 gmc envoy_slt
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2,548 Posts
I would suspect the front disconnect assembly is hanging up and needs attention such as more lubrication. They are known to have minimal lubrication.
 

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04 Trailblazer
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Discussion Starter #6
I would suspect the front disconnect assembly is hanging up and needs attention such as more lubrication. They are known to have minimal lubrication.
That's my thoughts also. I need to look at the front actuator correct?
 

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2004 gmc envoy_slt
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2,548 Posts
The actuator is probably OK since your switch light indicate correct selection and you don't have a Service 4WD light on. It is the actual disconnect assembly that is not moving correctly.
 

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2004 chevy trailblazer_ls_ext
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247 Posts
The disconnect is on the passenger side of the oil pan. Be careful when removing it. They like to seize to the oil pan and become difficult to remove. Try and work it out just a bit, then push it back into place. Try and work it out a bit farther, then push it back into place. Repeat the process until it comes out of the oil pan. Patience, young Padawan!
Otherwise:
End Well, this will not.jpg
 

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04 Trailblazer
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Discussion Starter #9
The disconnect is on the passenger side of the oil pan. Be careful when removing it. They like to seize to the oil pan and become difficult to remove. Try and work it out just a bit, then push it back into place. Try and work it out a bit farther, then push it back into place. Repeat the process until it comes out of the oil pan. Patience, young Padawan!
Otherwise:
View attachment 56555
Thanks for the heads up
 

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2002 chevy trailblazer_lt
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912 Posts
Before removing the disconnect, though it more than likely needs some attention, another thing you could try is this: remove the actuator, observe the plunger, you could even leave the harness connected and energize/denergize it so to see how the plunger moves. Having seen that see if you can use something like a screwdriver handle or such that is about the same size as the plunger and see if you can push into the disconnect where the plunger pushes.and see if the shift fork moves OK. It might require a small amount of rotation of the passenger side CV axle to allow the shift fork to move. You may find the shift fork doesn't move at all or it does move but the gears still don't engage.

This writeup here will give you a good understanding of what the disconnect does and how...

 

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04 Trailblazer
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Discussion Starter #11
Before removing the disconnect, though it more than likely needs some attention, another thing you could try is this: remove the actuator, observe the plunger, you could even leave the harness connected and energize/denergize it so to see how the plunger moves. Having seen that see if you can use something like a screwdriver handle or such that is about the same size as the plunger and see if you can push into the disconnect where the plunger pushes.and see if the shift fork moves OK. It might require a small amount of rotation of the passenger side CV axle to allow the shift fork to move. You may find the shift fork doesn't move at all or it does move but the gears still don't engage.

This writeup here will give you a good understanding of what the disconnect does and how...

TJ thank you for the link, I'll definitely check it out.
 

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2005 gmc envoy_sle
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7 Posts
There used to be a great flow chart, but can't seem to find it. Here is a good write-up to help you.

 

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04 Trailblazer
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Discussion Starter #13
There used to be a great flow chart, but can't seem to find it. Here is a good write-up to help you.

Thank you
 

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2003 gmc envoy_sle
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107 Posts
I use to have an issue like this once or twice at the beginning of winter. It did act like there was something that gets stiff as the weather got colder. When I was having the trans serviced I mentioned that the service 4WD light was on. When they test drove it there was no problem. Seems what little lube, is in the mechanism that's being talked about, warmed up by being inside, everything slid into place. I have gotten in the habit of switching to 4WD occasionally for a few miles once a week or so leading up to, and in winter. If I remember to do that, it never hangs up like you are describing.
 

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04 Trailblazer
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Discussion Starter #15
I use to have an issue like this once or twice at the beginning of winter. It did act like there was something that gets stiff as the weather got colder. When I was having the trans serviced I mentioned that the service 4WD light was on. When they test drove it there was no problem. Seems what little lube, is in the mechanism that's being talked about, warmed up by being inside, everything slid into place. I have gotten in the habit of switching to 4WD occasionally for a few miles once a week or so leading up to, and in winter. If I remember to do that, it never hangs up like you are describing.
I use to have an issue like this once or twice at the beginning of winter. It did act like there was something that gets stiff as the weather got colder. When I was having the trans serviced I mentioned that the service 4WD light was on. When they test drove it there was no problem. Seems what little lube, is in the mechanism that's being talked about, warmed up by being inside, everything slid into place. I have gotten in the habit of switching to 4WD occasionally for a few miles once a week or so leading up to, and in winter. If I remember to do that, it never hangs up like you are describing.
DDS, it's funny you say that. I had it into our local transmission and drive train shop and they found no issues either. Sounds a lot like what you are describing.
 
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