[Seth2013]

Hi All

This has been driving me nuts for a while how. I have a sierra transfer case which I have put 4.9 gears in and is now in my jimny, but its making some pretty bad noises. See video below



That is taken with the car idling in 4th gear with the transfer case in neutral, it will also do it in 3rd and 5th. it develops a vibration above 80 km/hr while cruising/coasting, but not under acceleration. the rattling noise in the video is definatley worse towards the top of the case.

Sofar I have shimmed the input shaft and replaced the uni joints in the jack shaft. I'm completely at a loss as to what it is, so I'm appealing to the internets for help

[AckerDackerly]

This is probably just a guess, but many of the vibration complaints that I have read about on the Interwebs turn out to be a broken, misaligned or worn transfer case mount.

Having said that, I suspect that something is out of place inside the transfer case. Of course, this is not what you wanted to hear that as it will require dismounting the transfer case and tearing it down to find where the mysterious noise and related parts wear is located.

I hope that this helps!

[MrRocky]

Jackshaft uni joint tight

[Seth2013]

AckerDackerly wrote:

Having said that, I suspect that something is out of place inside the transfer case. Of course, this is not what you wanted to hear that as it will require dismounting the transfer case and tearing it down to find where the mysterious noise and related parts wear is located.

I hope that this helps!

transfer case mounts are the indestructible ones from bigjimny so that rules them out and I had it apart last week to put the shims in, so not ideal, but if it has to be done - and I'm fresh out of paper gaskets. But I think you are right.

MrRocky wrote:

Jackshaft uni joint tight

Yeah they are tight, funny story that, I had originally installed them incorrectly but I fixed that up and they seem to be fine... Unless they bedded in wrong and screwed up. I'll take another video tomorrow, but I swear that Jack shaft is moving side to side. But I'm not convinced it's the source of all the problems, I originally did the uni's chasing this problem down, and the noise has stayed the same the whole time.

Other things I noticed when I had the case apart last week - the bearing on the back of the input shaft appeared to have marks on the outer casing as if it had been spinning- and it took zero effort to pull it out of the case. Other than that, everything else looked as good as it did when it got rebuilt.

[MrRocky]

Tight unis cause vibration and if you run a lowrange hd clutch or other aftermarket one then clutch chatter can be cause of the noise especially on decel. I had a slightly bent tcase arm that caused my case to be slightly noisy until swapped

[Seth2013]

Good news everybody

You got it I think MrRocky. I found a thread very late last night after some heavy googling which had multiple people having the exact issues in sierras after rebuilding with trail gear reduction gear sets. this was backing up what I had thought and my old man had suggested - the angle of the jack shaft to the transfer case input. So I just did some adjusting and the noise is essentially gone, as in good enough that I don't give a crap until it goes bang one day

Here is the new tweaked angle of the jack shaft entering the transfer case


I took one bush out of the back mount and added 2 steel washers and a rubber washer to get the bolt through the mount enough to bolt it up tight


and added the bush I pulled from the back to the front


I think maybe with some more tweaking I could get the noise out completely, but I'm pretty happy the way it is.

Big Thanks to the replies, its always very helpful!