98 Suburban 246 Transfer case clicking/popping

[ew0001]

I just recently bought a 98 Suburban to haul around the family. I noticed a popping/clicking noise coming from under the vehicle when in the neighborhood at slow speeds. I got up under the vehicle and it sounds like it is coming from the transfer case, near the tailshaft.

I read the other postings about the broken snap ring. I am not able to check on this model because the tailshaft housing is integral to the rear half of the case. I don't know if this model is susceptible to that as well.

Here's what I've gathered from the problem.

-Occurs only in 2wd mode, goes away in 4H or 4L.

-Sounds like to ball bearings impacting, or like a chassis frame popping/creaking.

-No rythmic or periodic pattern.

-With the rear axle jacked up and the transmission in neutral, the sound is easily reproduced by turing the driveshaft by hand, and sounds like it is originating in the transfer case. It is not speed depended.

-In 2wd, the noise occurs at light loads, or deceleration. Stepping on the accelerator makes the noise stop.

-It is a 246GM transfer case. I have 150,000 miles on the odometer.


Thoughts: The original owner had the transmission rebuilt. Is it possible the shop put the wrong fluid in it? Is there a re-learn procedure or adjustment for the encoder/stepper motor? The symptoms kind of sound like the shift fork is dragging and not retracted all the way.

Any thoughts, help, diagrams or troubleshoot procedures would be greatly appreciated.

-Ed

[Blue Bowtie]

New Venture 246 Xfer case? There is a TSB from GM regarding the noises from this box and the use of a newer (fully synthetic) AutoTrak II transfer case oil to solve it. IIRC, you will need about 2.9L of AutoTrak II (P/N 12378508) to change the oil.

[ew0001]

You are right... it is a New Venture 246. I got a little further on my problem. The sound was originating from the tailshaft area. I pulled the driveshaft and looked into the case through the rear seal and I noticed that all the ball bearings on the rear bearing are shifted to one side, or there are some missing. I also noticed what looked like a plastic retainer ring (maybe a bearing cage) loose around the output shaft. I noticed that there is a replacement driveshaft on the vehicle, so I wonder if the previous owner was out 4 wheeling one day, landed on a large rock, bent the driveshaft and broke the rear bearing cage. Does anyone have a picture of what the bearing should look like or how many ball bearings it should have? The noise was definitely the bearings smacking around against each other. I guess in 4wd, there is enough thrust load to keep them from crashing into each other. I also found out there is just plain ATF in the case, not the Autotrac fluid. I hope the clutches are ok. My plan is to take the transfer case out, change the bearing, put fresh fluid it in and hope for the best. The clutches seem to be ok. The 4wd works, and I don't plan on using it much. Thanks for the advice.
-Ed

[yo_11]

Same vehicle and same issue. Not sure if I have New Venture 246 or not; presume I do. I have vehicle @ friends tranny shop. I am going to ask him to service the transfer case with the AutoTrac II oil and go from there. Have you solved the problem yet?

[ew0001]

Yes, It was the rear tailshaft bearing. I split the case, replaced the bearing (which was obviously the issue), replaced the tailshaft bushing for good measure since it was doing most of the work, resealed the transfer case and put it back in. The noise is gone and it works like a champ. What a dumb bearing design... It has a plastic ball cage that snaps in place from the back of the bearing and nothing retaining it on the other side. If the plastic warps or you jar the driveshaft really good, it looks like it can easily pop the cage loose. What I figured was that when you place the vehicle in 4wd, it loads the clutch pack, which loads the bearing and keeps the loose ball bearings from smacking into each other. That is why it made noise when coasting in 2wd. Also, GM thinks very highly of their two output shaft seals. They were over $60 each at GM. I didn't have much luck finding them elsewhere. I did use GM's AutoTrak fluid. Let me know if this is your issue, or if you need advice.

[yo_11]

Thanks for the update. Just got off the phone with the transmission shop right after reading your post. Verdict is in for me as well: Tailshaft Bearing. It's good to hear that your fix for the problem was successful. Had I known, I probably would have attempted to fix myself (with a little help). Replacement bearing set they're using has a metal cage. Total fix is ~$700.
Will

[ew0001]

Who did they get the bearing from? I sure would have preferred a metal caged bearing..... Was it in an entire rebuild kit?

[yo_11]

Pretty sure it was a bearing kit - they replaced them all. I'll try and find out where they get them from and post it later.

[Borguy]

I think I have the same problem on my '99 Suburban.
Exactly the same clicking sound when you get off of the accelerator.
Also found myself underneath trying to figure out where that noise came from.

I would like to replace the bearings myself but I'm not sure if you can split the TC without lowering the engine+trans. It seems there might be a (rivetted) piece of the frame in the way ??
And does it split without dropping several pieces??

@ew0001 : any hints, help.


Greetz,

Borguy (Belgium)

[Borguy]

Could anyone please post a tech drawing of a '99 (model '98) T-case.
I'd like to see what I am going to find when opening the thing.
Thx.

[Blue Bowtie]

Check here:

http://www.rsgear.com/NV246.htm

[Borguy]

@ Blue Bowtie : Thx

I've ordered a new tailshaft bearing (€80) and bushing (€100) at a GM shop.
With taxes it will come to approx. $260

I've read somewhere that you should put a NV246 T-case in neutral before splitting it. Are there any other things I should keep in mind when I start on it?
I hope no other things went bad inside cause I kept driving it ...

Thanks.

[Borguy]

I've started on splitting the T-case but soon found out that the crossmember which holds the torsion bars has to be taken out in order to get the T-case far enough backwards.
But after trying for more than 3 hours with different kinds of tools it won't work
Do I have to disassemble part of the front suspension to lower the torsion on these bars? In my opinion that's the only way .... ??

Another possibility is to take the entire T-case out and in that case I have to take another crossmember out but this one only supports the T-case.

If I try this then I have already a next question:
Which part do I take off ? Only the T-case or also the part between the transmission and the T-case (15-20cm approx.)
Does it slides off or what is the next catch...

Thanks for any help, burb is out and now I have to drive my wive's Toy starlet ...

[Borguy]

Did a search on "torsion bars" and found the procedure.
Will try it this evening. First have to get me the right tool..

[MT-2500]

Originally Posted by Borguy

Did a search on "torsion bars" and found the procedure.
Will try it this evening. First have to get me the right tool..

I would suggest removing the transfer case instead of torsion bars or cross member. It is a pain and sometimes impossible to get torsion bars or cross member out.
This link covers transmission repair but also covers transfer case removal.
http://72.19.213.157/files/4L60ERepairs.html