correct 4wd operation?

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Original poster
Member
Aug 25, 2012
955
Hey all, I just want to double check with everyone on whether or not my 4wd is operating properly.

I have my truck up on 4 jack stands in the driveway since I have been cleaning up the frame and I put POR15 on it to try and slow down the rusting on it so I can get hopefully 6 more years out of it before I need to toss the truck. Anyway, I wanted to double check the operation of the 4wd and here is what I found.

1.) I have no CEL codes or service 4wd codes, when I turn the 4wd selector switch, everything changes like it should when I put it between 2wd, a4wd, 4hi, 4lo, n.
2.) I had placed the truck in 2hi and put it into gear and only my left rear wheel spun (that part I know is normal because I don't have a LS or a locker in the rear diff)
3.) I stopped the wheel with the brakes and then switched to 4hi and put it back into gear. When I did this, the left rear wheel was spinning but neither of my front wheels were spinning. I could hear a little grinding noise that can be best described as when someone grinds their gears when shifting a semi
4.) I stopped the wheel and placed my truck in 4lo and then back into gear and neither front wheels were spinning and the same gear grinding noise was present.
5.) While the rear wheel was spinning freely, I decided to grab my front tire and move it and if I move it, the grinding noise goes away but as soon as I stop the wheel, the grinding noise comes back.
6.) The front and rear driveshafts were both spinning in 4hi, a4wd and 4lo so the transfercase seems to be functioning as it should.
7.) I know this part is not recommended at all but a few months ago I placed my truck in 4hi and turned into a parking spot and you could feel it getting bound up like 4 wheel drive normally does when you turn the wheel sharp. I only did that until I felt the binding and then switched back to 2hi and everything was fine.

Does this sound like normal operation of the 4 wheel drive or do I have a toasted front diff?
 

Sparky

Member
Dec 4, 2011
12,927
Sounds like between a few months ago and now, your splined disconnect has bit the dust, or the actuator has. Pull the actuator and make sure it moves properly, if it does then there is likely something going on inside the disconnect. How many miles on the truck?

What you did is a common way of testing 4x4 function. As long as you aren't forcing it you're not going to hurt anything.
 
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kickass audio

Original poster
Member
Aug 25, 2012
955
Well I had went to play with it some more after my first post and the stupid splined disconnect is to blame. It is shifting from what I can hear when I engage it. I didn't take the actuator off because I was afraid of something falling out or it breaking on me.

I had found in the early spring that my CV axle near the disconnect has more play than it normally should have so I know the bearing in there is on its way out and don't feel like repairing the stupid thing and certainly don't want the expense and aggravation to remove the whole unit which is always a PITA from what I have seen on here. Anyway, I grabbed the inner part of the CV shaft and if I wiggle it around the 1/8" it moves, I can eventually get it to engage and it works just fine. If I move it back to 2wd, it disengages without any hitch. If I put it back into 4wd, sometimes it engages fine, otherwise it sounds like it engages but it isn't actually engaged. When i wiggled the CV shaft, you could hear the click of the fork engaging in the disconnect so I don't think the actuator is bad, maybe just the age of it with the old/dirty grease in it is causing it to bind up.

My truck has somewhere around 138k miles on it. I recently upgraded the instrument cluster and didn't pay to get the mileage corrected so I have 30k more miles on the odometer than are actually on the truck.

edit: I was playing with it some more and found that from what other people mention of the gears not lining up internally when they engage the actuator, they move the wheel side to side a bit and it engages. Sure enough I did that and it always engages when I do that. If I leave the wheel alone, sometimes it will engage and sometimes it will not click into gear for the disconnect.
 

Sparky

Member
Dec 4, 2011
12,927
That makes sense because of how often the gears are perfectly in line for the collar to just slip over (almost never). That said, if you're noticing play now it'll just get worse. I'd fix it before it gets past fixing, and/or leaves you without 4WD this winter. I'd rather deal with the aggravation now while the weather is decent than later when the weather sucks.

I prefer to rebuild as it is cheaper and I know what kind of grease I'm putting in it after rebuilding, but that said the OEM does make it over 100k miles in most cases and it is a one time repair for the majority of people. Just getting a whole unit, while more expensive, is a fair bit easier to do. And if you're one of the unlucky ones that the housing breaks on (like me) then it wouldn't matter since you have an entire unit waiting to be installed anyway.
 

kickass audio

Original poster
Member
Aug 25, 2012
955
Honestly, I only used 4wd twice last winter and those times were because I buried my truck up to the frame in a snow mound on the street so I could be out of the middle of the road when plows went by in order to avoid getting clipped by the plow. I was just curious on it's operation with how it worked. I still think the disconnect design we have is one of the dumbest things ever and as usual, GM engineering has it so my tranny lines run right in front of the damn thing and it is notably a pain in the *** to get the disconnect off the oil pan.

I just really wonder if mine is just loaded with old grease and if I can take half of it off while it is on the truck to clean up as much of the old grease I can and then put it back together. I wish I was at work this week so I could go to my coworkers envoys and hear how theirs engages into 4wd. When I move the wheel to get the fork to align into the gears, it's no more than the width of your finger that I rock the wheel to get it to engage.
 

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