Help me identify this noise! Now with a video!

[Chevy305]

Ok I am getting what best can be described as a gear chatter like rattling type noise coming from my drivetrain somewhere. Its kinda loud and hard to miss. Its tough to pin point exactly where its coming from but I am suspecting the t-case.

The noise comes around when I hit the shift point of each gear and then goes away as I climb the next gear until i am ready to shift again. Also on the highway when I am in 4th and spinning at least 2500rpm and up if I am just cruising the chattering will start to come back. If I let off the gas it goes away and if I accelerate it goes away.

The u-joints are not the problem because i already replaced them. Can somone help me figure out what it is, and how to fix it?
305/SM465/208/10bolt

 

[55Willy]

does it make the noise with the t-case in neutral?

I'm guessing something in the case cut loose when the shaft parted ways.

 

[Chevy305]

does it make the noise with the t-case in neutral?

I'm guessing something in the case cut loose when the shaft parted ways.

It only does this when I am driving down the street. I can try that tomorrow sitting in my driveway with the tcase in neutral and I can cycle through the gears like normal and see if the sounds comes up.

But also this winter when driving in the snow in 4hi the noise was still there.

 

[55Willy]

has the T case ever "popped" out of gear? maybe it's not hitting each detent so it's like half way in gear in the t case????

 

[Chevy305]

has the T case ever "popped" out of gear? maybe it's not hitting each detent so it's like half way in gear in the t case????

No never has.

The only time the t-case has ever done anything weird was when I let it run low on fluid and I went offroading with it. It sounded kinda grindy so I added fluid and it was all good. Afterwards there were no unsual noises.

Maybe that little stretch with low fluid ruined something in it thats causing this noise?

 

[obijuan]

i was experiencing the same thing just a few days ago, my slip yoke was cracked. very unusual but it was. also my cv guts parts were worn out.

 

[Chevy305]

I'll take the driveshaft out and inspect the yoke...

 

[jimmyjack]

Remove your inspection cover and check the flex plate. My blazer used to click and chatter but only when I drove it. Turned out the flex plate had a crack around every bolt in a complete circle. Good luck....

 

[Chevy305]

Remove your inspection cover and check the flex plate. My blazer used to click and chatter but only when I drove it. Turned out the flex plate had a crack around every bolt in a complete circle. Good luck....

I don't have a flex plate... SM465 is a standard...

Even so I can't see any flywheel cracks since my truck doesn't have an inspection cover. And besides that would cause a separate issue.


As far as testing the truck with the t-case in neutral, I did not hear the chattering sound at all. I even used a stick to hold the throttle at highway cruise speed in 4th gear while I went under the truck but there was nothing out of the ordinary.

I also inspected the yoke and it is in good shape. No cracks or anything. It still mates securely with the tail shaft of the t-case.


So then to me this seems like its an internal tcase problem...

 

[obijuan]

i hope not! i really do!

 

[warrior454]

Been fighting that same issue for a year now have tried 3 different T-cases
rebuilt the tranny had the motor apart tried driveshaft from a friends K5
torn the Diffs apart and put all new bearings in them cant get rid of it no how
sometimes its worse then others usually going home from work
and sometimes getting a vibration with mine
i have a 700r4 with a 454 in mine

 

[Chevy305]

Been fighting that same issue for a year now have tried 3 different T-cases
rebuilt the tranny had the motor apart tried driveshaft from a friends K5
torn the Diffs apart and put all new bearings in them cant get rid of it no how
sometimes its worse then others usually going home from work
and sometimes getting a vibration with mine
i have a 700r4 with a 454 in mine

Wow I hope can fix it some how...

 

[Chevy305]

I've been thinking and, could this be a bad pinion bearing?

 

[jonrpick]

I've been thinking and, could this be a bad pinion bearing?

That's the problem I have. The fact that the noise is there right before the shift kinda makes me think it's a bearing. Before the shift, the drivetrain is under load, but right at the shift it momentarily relaxes. My rear pinion bearing is shot. When accelerating or slowing down I don't have the noise that much. When I try to maintain even speed on a flat grade, it's unbearable.

I noticed it on my shifts yesterday on the trip home. Also, when the tranny would kick down to a lower gear or unlock the converter, I'd hear a quick "thunk".

I had a similar problem with my Dodge Van but never traced it down.

My vote is a bad bearing.

~jp

 

[Chevy305]

Update w/ videos

I tooks some videos of the noises today.

If you turn up the volume you can here it in the background. I am in 3rd gear btw.
http://www.youtube.com/watch?v=3xSGPxzwUHQ



This one is a relatively new sound, I think it came about since I am driving on the highway a lot more now. I also tried it with the t-case in neutral and the trans made the same sound. The engine is idling in 4th gear:
http://www.youtube.com/watch?v=c-CnMW8BLGY

 

[Chevy305]

ttt

 

[SnackPack]

You tried the same thing as in the last video, but using a length of tube to your ear as a stethoscope? Also try a long screwdriver with the handle on your ear?

 

[Chevy305]

You tried the same thing as in the last video, but using a length of tube to your ear as a stethoscope? Also try a long screwdriver with the handle on your ear?

damn i should have done that...