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2002 chevy trailblazer_lt
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A Related Problem?

Hey guys!

I've been reading this and several other threads in anticipation of repairing my front axle actuator housing while replacing my engine in the very near future. It just dawned on me that my engine failure might be DUE to the front axle actuator housing failure!

Let me explain: Last summer, I began hearing a rattling sound from the pass. side while rolling at any speed. I suspected it was the front wheel bearing assy, bought the part, and began the teardown to replace it. It was then I noticed the play and SEVERE wear in the axle actuator housing.
Now, my 4WD hasn't worked since I bought the TB used in 04, much to my chagrin. (I "tested" the 4WD by shifting it to 4LO while test driving it, and assumed since I felt it shift into the lower range that everything worked. Imagine my surprise, and cursing, that winter!) I put off fixing it until I had the "time and money", which, as many of you know, never really happens! Anyway, the housing and bearings were completely dry, and had worn to the point that the tail of the CV shaft was banging around inside the housing, causing my rattle.
Keep in mind I was working on this in my driveway, on a Sunday, and I would need to drive the TB to work Monday morning. So, I removed the pass side CV axle to eliminate the noise and any continued damage. Problem solved until I could replace the housing assembly and axle, right?
Everything seemed fine until September, when I began to hear what sounded like a rod knocking in the engine. During a test drive to figure out exactly what the noise was, the TB experienced a banging sound followed by a complete loss of oil pressure, and then the engine dying. The engine is not locked up, and will turn over and try to start, but runs very rough. I have 180K on this engine, so figured now was a good time to replace it.

Now, I'm wondering.....is the intermediate shaft supported on the pass side by that actuator housing? And, if the bearings are completely shot in that housing, does the intermediate shaft flop around? And could that be the cause of my engine damage? I have no oil leaks, nor any loss of oil.
 

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2004 chevy trailblazer_ls
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Yes, the 4WD disconnect assembly has a needle bearing that supports the intermediate shaft and the gear that it slips into inside of the disconnect. Now, has far as I know, the intermediate shaft just passes through a tube cast into the oil pan...so unless the shaft flopped around enough to break or damage the oil pan in some way I don't think that could cause any direct engine damage.

Now, I'm wondering.....is the intermediate shaft supported on the pass side by that actuator housing? And, if the bearings are completely shot in that housing, does the intermediate shaft flop around? And could that be the cause of my engine damage? I have no oil leaks, nor any loss of oil.
 

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2005 chevy trailblazer_ls
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After all my months of researching this issue, I just NOW found this thread! Anywho, I'm pretty sure that I have narrowed it down to the actual disconnect itself. Here's my issue.

There has never been any type of indication (4DW light, fault in switch light, etc) other than normal from the dash. I always select 4WD at a stop in neutral. I select any mode, and I can aurally hear the motors moving, and see the switch blink while in transition (~5 secs?). When I go to put in drive, the truck hops forward (moreso in 4LO), as if it has engaged. However, there doesn't seem to be any power to the front wheels. When I do drive with the switch in 4HI, I can hear an ever so soft/smooth grinding in the front end. This leads me to be it is not electronic, nor the transfer case. Can someone confirm my hypothesis, so I can git-r-done! (now that the snow has melted!)
 

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After all my months of researching this issue, I just NOW found this thread! Anywho, I'm pretty sure that I have narrowed it down to the actual disconnect itself. Here's my issue.

There has never been any type of indication (4DW light, fault in switch light, etc) other than normal from the dash. I always select 4WD at a stop in neutral. I select any mode, and I can aurally hear the motors moving, and see the switch blink while in transition (~5 secs?). When I go to put in drive, the truck hops forward (moreso in 4LO), as if it has engaged. However, there doesn't seem to be any power to the front wheels. When I do drive with the switch in 4HI, I can hear an ever so soft/smooth grinding in the front end. This leads me to be it is not electronic, nor the transfer case. Can someone confirm my hypothesis, so I can git-r-done! (now that the snow has melted!)

Sounds like mine did when it failed.
 

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Ok, that boosts my confidence a bit. I'll probably just order the seals, bearings, and the fork from GMparts or parts4chevys. They have pretty decent return policies. Just out of curiosity, what exactly did you replace, and what was busted? Thanks
 

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Ok, that boosts my confidence a bit. I'll probably just order the seals, bearings, and the fork from GMparts or parts4chevys. They have pretty decent return policies. Just out of curiosity, what exactly did you replace, and what was busted? Thanks
To boost your confidence a bit, follow the flowchart on this thread: http://www.offroadtb.com/articles/tech-docs/what-is-wrong-with-my-4wd-system to help determine what part you should examine.

However, from what you're saying, I'll agree with Fishsticks, probably something in the actuator. You can help yourself determine what went wrong by going under your vehicle and vigorously jiggling the passenger tripod housing. If it moves more than 1/16", your bearings probably seized. If it's fairly solid, you may have a broken fork.
 

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To boost your confidence a bit, follow the flowchart on this thread: http://www.offroadtb.com/articles/tech-docs/what-is-wrong-with-my-4wd-system to help determine what part you should examine.

However, from what you're saying, I'll agree with Fishsticks, probably something in the actuator. You can help yourself determine what went wrong by going under your vehicle and vigorously jiggling the passenger tripod housing. If it moves more than 1/16", your bearings probably seized. If it's fairly solid, you may have a broken fork.
Great thanks. I have followed that chart a while back, and came to the conclusion that it was the front end. Ill try your tricks to narrow it down!
 

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2003 chevy trailblazer_ls_ext
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Why does it need to be separate from the oil pan in order to use gear oil? The front diff isn't separate, and it uses gear oil.

I've considered adding a fill plug and a drain plug, and just going with a heavy gear oil. Why do you think it is not possible?
Yea it probably would with a vent installed, it has to be able to vent or it will push oil past the seals or suck water in, and there would only be a very small amount of oil in it. And we all know the way the diffs never get checked for oil, I think grease would be the better choice for this particular application, :m2:
 

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Hello again. Im bringing this thread back, as the winter is coming and I need to get my 4WD fixed! I believe I have ruled out the actuator, as I removed it, and it appears to be working fine. Retracted in 2HI, and extended in AWD, and 4HI. I reinstalled it, and it sounds like it is still working. I took these pics below, showing the amount of play on the right front axle. The first pic is one of the axle at rest, and the second is me pushing up on it. It has a lot of play, and there is definitely something clunking around in there. The movement if more drastic in person, but I'm sure the picture reflects it. I'm no engineer, but if I were to guess, this shouldn't be moving at all. I assume its one of the first few bearings. I am trying to clearly identify what part it is, because this is my daily driver, and I don't want to tear it down, just to find out the issue, then reinstall it to tear it down again. I could buy everything, but I'm not sure the return police on GM parts etc. As always, thanks for the info!
 

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Discussion Starter #72
I believe I have ruled out the actuator, as I removed it, and it appears to be working fine. Retracted in 2HI, and extended in AWD, and 4HI.
Not totally ruled out, as I've seen two actuators on friend's trucks that worked fine outside the vehicle, but didn't have the full torque available to push in the fork spring. One cleaned up nicely since the problem was grease on the sliding contacts, and the other one was a low torque motor that didn't work well when cold.
I reinstalled it, and it sounds like it is still working. I took these pics below, showing the amount of play on the right front axle. The first pic is one of the axle at rest, and the second is me pushing up on it. It has a lot of play, and there is definitely something clunking around in there. The movement if more drastic in person, but I'm sure the picture reflects it. I'm no engineer, but if I were to guess, this shouldn't be moving at all. I assume its one of the first few bearings. I am trying to clearly identify what part it is, because this is my daily driver, and I don't want to tear it down, just to find out the issue, then reinstall it to tear it down again. I could buy everything, but I'm not sure the return police on GM parts etc. As always, thanks for the info!
That's horrible movement. You need at least the two outer bearings and seal. And the damage has allowed crud to get in there so the extent of the internal damage can't be known. You should probably just buy a new unit and swap the whole thing at this point. There's an aftermarket one on the market now for a little bit less than GM. Junkyards might also score one for you.

Your CV shaft might have damage in the bearing region as well.

If you insist on taking it apart and only buying the parts that are toast, you're going to need another DD for a while.
 

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Not totally ruled out, as I've seen two actuators on friend's trucks that worked fine outside the vehicle, but didn't have the full torque available to push in the fork spring.
Ok, yeah I remember you talking about (Teebs I think it was) your friends TV that had the same issue. I am basing this on the fact that when re-installed, their is no change in sound (ie no stress on motor and nothing abnormal). It wouldn't be the first time I am wrong however.

Your CV shaft might have damage in the bearing region as well.

If you insist on taking it apart and only buying the parts that are toast, you're going to need another DD for a while.
I'm praying their is no damage to the CV shaft, but I will probably be safe and just order all the parts in the disconnect. If I have it open, I might as well re-build the whole thing, seeing that different parts (bearings and fork) have had their different issues. I don't have another DD unfortunately. I think when I looked up the parts months ago, I'd be out a little under $300.

Thanks as always Roadie.
 

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One more thing Roadie. What do you think the chances that the Outer and Inner Shaft Gear (12471628/12471627) would be the culprit? It seems the majority of issues are worn bearings, and a broken fork. I would like to avoid ordering these parts, due to their cost, and the good chance that I will not need them. By the schematics, it looks like these gears are pretty wel protected inside the shift collar. All the bearings, fork, and washers are not a problem, but if the gears are going for $75 a pop, I would like to avoid that expense.

Thanks again!

ARL
 

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Discussion Starter #77
They're probably not worn out, but really, there are going to be no guarantees from folks who aren't there. Just guessing. That was a LOT of bearing movement. Wish you had found it in a regular inspection instead of letting it go so far. :cry:
 

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One more thing Roadie. What do you think the chances that the Outer and Inner Shaft Gear (12471628/12471627) would be the culprit? It seems the majority of issues are worn bearings, and a broken fork. I would like to avoid ordering these parts, due to their cost, and the good chance that I will not need them. By the schematics, it looks like these gears are pretty wel protected inside the shift collar. All the bearings, fork, and washers are not a problem, but if the gears are going for $75 a pop, I would like to avoid that expense.

Thanks again!

ARL
If you end up needing one or both, you have another option. Remove the fork, collar and both gears and buy the one piece sleeve from an AWD truck. Your front axles won't disconnect ever again (slight loss of mpg) but you won't be fixing this again in a few years either. :)
 

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One more thing Roadie. What do you think the chances that the Outer and Inner Shaft Gear (12471628/12471627) would be the culprit? It seems the majority of issues are worn bearings, and a broken fork. I would like to avoid ordering these parts, due to their cost, and the good chance that I will not need them. By the schematics, it looks like these gears are pretty wel protected inside the shift collar. All the bearings, fork, and washers are not a problem, but if the gears are going for $75 a pop, I would like to avoid that expense.

Thanks again!

ARL
I had a very small amount of movement and one gear needed to be replaced, due to the bearing surface spalling off.
My shift fork was ok untill I put it back together and over greased it and the fork was not able to slide all the way and started to wear off.
 
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