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Registered
2002 chevy
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83 Posts
Discussion Starter #1
Hello
I need some help from Trailvoys experts with a diagnose.

I have a sound i belive is coming from the transfercase, possibly a bearing.

It sounds awful and kind of embarrasing to drive around with this noise.

I've heard about a bearing that is going out on TC:s with frekvent use of A4wd, does anyone know what bearing that is?.

I think i have little to much play in the outgoing shaft to the front wheels(up and down), maybe its these bearings that use to fail.

They seems fairly easy to change to me, not involving the more advanced parts of the TC.

the noice has been there for more than a year now and has not gotten any worse over time.

It is only heard when in 4wd and in A4wd when it engages wich you can hear in the video.
Everything works as it should, no other problems than this awful sound.

The TC is supposed to be changed to this used one 12000km before i bought it.

I have changed the fluids in TC and rear and front diff the first thing i did when i bought it Nov 2009 , as it was close to the 100,000 mile service anyway.

Thanks for any input. :tiphat
http://www.youtube.com/watch?v=SuGFjcUoZ3k
 

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Registered
2002 chevy
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83 Posts
Discussion Starter #2
No one has any ideas??


How much radial play is normal at the outgoing shaft to the front diff??


The sound is the same when acc or dec or coasting.

Please, anyone with any ideas what to start looking.


How much extra noise is normal when in 4WDhi, TB:s are not that common here in Sweden so i cant really go to a cardealer to do a testdrive unfortunatley.
 

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Banned
2004 gmc
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26,181 Posts
There should be almost zero play in any driveshaft. Sounds like a bearing to me, but that's difficult to be sure of. I would get it on a lift, run it the same way with the wheels off the ground, and have a mechanic listen with a stethoscope and confirm the exact source of the noise.
 

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2002 chevy
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83 Posts
Discussion Starter #4
Ok thanks Roadie i will do that.

Do you have any idea on what bearing there is that go bad on these TC:s most frekvent.
I think i read somwhere about that but cant find it again, I spent last night reading almost every post in the 4wd drivetrain section:sleepy:

The TC has been changed out to a "new" one so i have no idea what year the TC comes from. Is there anyway to determin what year by any number anywhere.


One question though, when in A4wd the clutches is engaged about 5% as i understand. Will that be enough to make the front shaft spin??. Why i ask this is because when in A4wd(but not engaged) i have a very faint similar sound as you can hear in the video. Its to quiet to hear in any video recording but still its there.
 

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Banned
2004 gmc
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26,181 Posts
Most owners simply replace TC with junkyard ones, so almost nobody rebuilds them due to the expense of paying a mechanic. And most DIY owners do not have the time or skills for rebuilding differentials or transfer cases.

So I don't have any data on which bearing is more likely to fail. Sorry.

The driveshaft will indeed spin in A4WD mode, but it's not actually spinning because of the 5% torque from the TC clutches. This has two major effects.

1) The bearing out of the front of the transfer case is going to be spun up, and may make noise.

2) More parts are spinning in the front differential.

In 2HI mode, the driveshaft is not spinning. But the driver's side CV shaft IS. The CV shaft turns a main gear, but since the carrier is not spinning because the ring gear is not spinning because the pinion gear is not spinning, this means the main (end) gear turns the spider gears. The spider gears transfer their motion to the passenger's side main gear, which (because it's an open diff with the carrier not spinning) turns the passenger side intermediate shaft BACKWARDS. It's because of this that it's not entirely safe to engage A4WD while driving at speed down the road. The sliding collar on the splined disconnect will be connecting two gears that are spinning OPPOSITE to each other at road wheel RPM. Not much mass behind it, but there's some.

In A4WD and 4HI and 4LO mode, the CV shafts on BOTH sides are spinning at road RPM, the carrier is also spinning, and that drives the ring gear which drives the pinion gear which rotates the driveshaft all the way back to the TC.

Your noise may be coming from the front diff or its bearings or internal parts, whcih is why it's essential to get it on a lift and listen close-up.
 

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2002 chevy
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83 Posts
Discussion Starter #6 (Edited)
So if i understand this correctly, the front wheels is is turning the driveshaft when in A4wd mode when clutches is not(5%)activated, right?.

What if a bearing in the diff would be bad, wouldnt that make almost as much noise in this mode as in 4wdhi then. I would have understand this if the sound only comes when accelerating or decelerating(putting some tourqe on it) but it is the same all the time in 4wdhi or lo.
As you can hear in the video its silent in A4wd until i spin the rear tyres and it engages fully.

I will take it up on a lift for a closer inspection but i like to exchange some thoughts before that to maybe come closer to a solution if you dont mind me asking .
 
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