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05 trailblazer front axle disconnect possible problem help!

22K views 7 replies 4 participants last post by  Martinez218  
#1 ·
I have an 05 Chevy Trailblazer with 145k miles. I went to take the truck out 4 wheeling. All the lights on the switch work fine I can hear all the motors for every 4x4 option. But only awd seems to be actually working and locking the front tires. I'm almost sure it's the front axle disconnect because I can wiggle the CV axle and it has a lot of play and is also making noise like rattling when I'm driving. I found a flow chart on how to see what's wrong with your 4x4 I lifted the truck and it all pointed to the front axle disconnect do you guys have any opinions? It's an expensive part I don't want to buy it before I make sure that's what's wrong
 
#2 ·
I think you need to raise the front of the truck and verify if both front wheels are engaging. You mention AWD, do you mean AUTO or 4Hi?

The front disconnect when engaged, splines the passenger side axle to the differential. If there is an issue with the front disconnect not engaging, you really won't have ANY form of 4WD. When you have the front of the truck raised, place the selector in AUTO. If you spin one of the wheels in one direction, the other wheel should spin opposite. If it does, then the disconnect is engaging. If your selector is in 2HI, each of the front wheels will spin independent of each other.

By the way, the electronic disconnect module is a common failure on these trucks. And the disconnect unit is also prone to failure because it is only packed with grease. It is separate from the front differential and is not filled with gear oil. The passenger CV axle will normally have some play in it, but if excessive, it's likely the bearings and seals are worn.

The disconnect unit is rebuild-able, can install new bearings, but by the time it becomes evident that there is an issue, the bearing races have probably spun in the housing and new bearing races will not have a tight fit. Consider pulling and repacking these units with grease a maintenance item on these trucks.
 
#3 ·
Sorry, forgot to mention, when spinning the front wheel to see if the front disconnect is engaging, have someone help and hold the front driveshaft to keep it from spinning.

If the opposite wheel doesn't turn then it could also be a problem in the front differential as well as the disconnect unit. If the other wheel spins opposite, then you have to set the sellecter to 4HI. That should prevent you from being able to turn the front driveshaft. If the front driveshaft spins in 4HI then the problem is in the transfer case or the transfer case motor (encoder). By the way, do these checks with the truck in Park.
 
#4 ·
Yea sorry I meant the a4wd I heard it's like awd but i found a diagram on this forum like your explaining i put the truck in 4 hi raised the passenger side and only that tire spun. Then raised both and spun it again and nothing happened. I didn't try that again in a4wd. When I went out 4 wheeling I put it in a4wd and I could litteraly see the front wheels spinning and grabbing so I put it in 4hi and 4low did the same hill and nothing was working but my back tires. And like I said not only is there a lot of play right near the disconnect there is also a loud metal noise coming from the passenger side wheel everything else is pretty much brand new on the truck for the front suspension.
 
#5 ·
Sorry I forgot to add whenever I was doing the test I raised the passenger side put it in 4 high the drive shaft did not move I raised up the driver-side and passenger-side put it in 4 high spun the passenger tire and neither the other Tire moved or the drive shaft
 
#6 ·
Well if putting it in 4HI locks the front driveshaft, than likely the transfer case and the transfer case encoder motor are engaging. The problem could be the front disconnect actuator (the electronic black module bolted onto the face of the actuator assembly), the disconnect assembly itself, or the front differential (although if it were the front differential you would probably have a lot more symptoms).

Both the actuator and the disconnect assembly are common failures. In your case it sounds like the actuator may not be fully engaging and you may also have bearing failure in the disconnect assembly.

When switching from 2HI to AUTO, you should hear the motor in the actuator engage for about 2-3 seconds. If it is short and abrupt, it is only partially engaging. If my memory serves me, there is a little electric motor inside the actuator with a worm gear. The motor may be getting weak or the grease on the worm gear has dried up. On one of my previous TBs, I was able to crack the actuator assembly case open (held together with RTV or some sort of sealant) and simply re-greased the worm gear and I got it to function again. If you think that you did have some operation of 4WD, than this is an intermittent condition and the actuator is likely the failure.

The disconnect assembly has a fork with a splined collar that moves back and forth when engaging 4WD that basically connects the passenger CV halfshaft to another shaft that goes through the oil pan that connects to the front differential. This is what mechanically engages the two front wheels together. If not engaged, the shaft that goes through the oil pan will free spin when 4WD is selected and no power will be transmitted to the front wheels. Although, in your case, I would start with checking if the electronic actuator is fully engaging first, that's most likely.

Now, the disconnect assembly is a bad design, because of the height of the motor, they had to drop it such that the oil pan is in the way between the differential and passenger side axle. The disconnect assembly is insufficiently lubricated to last the life of the vehicle, it does not contain gear oil. Bearing failure is very common. This will result in a lot of slop in the CV axle, but keep in mind, there is some sideways movement in this axle, even when the disconnect assembly is in good shape. It sounds like in your situation, you may have both an issue with the actuator and bad bearings. Although, even with bad bearings, as long as the internal fork is not broken or the internals including the collar are not destroyed, it should still engage 4WD. That's why you need to verify the actuator first. But if you suspect bad bearings, don't let it go too long, because you may be able to rebuild the unit. Once the races spin in the housing, they start eating away at it. And, you could be destroying the bearing surface of the axle shaft.

Do some google searches on 4WD disconnect rebuild. There's lots of information on this because it's so common.
 
#7 ·
Hi I am new to this forum. I am having issues with my 2004 envoys 4 wheel drive. It makes noise in the front passenger side. And it seems to have some resistance and not alow the vehicle to move. And when it is disengaged it makes a bad pop noise. The Envoy runs good in 2hi. It only does this when in 4x4.