Bad Noises, T-Case?

5gn-h3t · Dec 20, 2016

Writing this on my cell phone on break at work so bear with with me.

2006 H3, stock, 192k miles

Im getting a horrible bang/clunk every few minutes then it might go away for a few miles. Feels like running over a parking block. Scary enough that I stopped driving it. Sometimes the traction control even kicks in. I pulled the front driveshaft and dove it around. The bang wasn't as pronounced but now I also have an occasional decel grinding/squeal. Drained both diffs and t-case. Fluids look normal. They were all changed inthe last year. Feels like it is coming from the t-case area. Not sure if I should pop open the front diff first or just drop the t-case. With the driveshaft in, it was also much worsein4-lock.

Any thoughts? Thanks in advance.

08H3 · Dec 20, 2016

I would guess the snubber in your transfer case came loose and periodically gets caught between the chain and sprocket. Diff would likely be a persistent noise.

EDIT: Just noticed you had an '06. Some -- maybe all '06s did not have the snubber from what I know, so I may be wrong. Good luck figuring it out.

alrock · Dec 20, 2016

Start with that diff crossmember, it's almost always the first drivetrain clunk. Noise travels - make sure your front suspension pieces are tight, from upper a-arms to lower to steering rack (okay, the last one isn't exactly suspension.) It could be a transfer case issue but that's harder to diagnose, so start with these visible pieces first.

4speedfunk · Dec 21, 2016

My guess is something is loose inside the t-case. My 08 had the same exact problem. It turned out to be the snubber bouncing around inside.
A worn chain will also cause this...they can get so loose they actually jump a tooth. It's very harsh and feels like you got rear-ended. It usually happens on accel or decel, and under 30 mph. At cruising speed, the chain seems to stabilize, and stays put. You should pull the t-case, separate the halves, and have a look. 192k on a BW3393/4 is about triple the life of the chain.

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06 H3 · Dec 21, 2016

Pull the front diff cover and check that out, check all exterior things like diff bushing, a arms like alrock said...from there look at t case and rear diff. They are the most stout so look at those last. These damn t cases are sensitive to fluid changes. They seem stout if you constantly change fluid in em. Most that break are neglected of fluid change

alrock · Dec 21, 2016

Agreed on the fluid changes. I'm setting about a 10K or less fluid change schedule on the t-case.

5gn-h3t · Dec 22, 2016

4speedfunk said:
It's very harsh and feels like you got rear-ended. It usually happens on accel or decel, and under 30 mph. At cruising speed, the chain seems to stabilize, and stays put. You should pull the t-case, separate the halves, and have a look.

This describes it perfectly. Its fairly violent. Happens much more in stop-go traffic than it does on the highway. I know what I'm doing on christmas break. Thank you everyone!

06 H3 · Dec 22, 2016

alrock said:
Agreed on the fluid changes. I'm setting about a 10K or less fluid change schedule on the t-case.

I'm about that time frame too. At 15k it still was pretty dark. I'll try 10k now...not sure what the hell goes on inside that causes the fluid to get so dirty

08H3 · Dec 23, 2016

I've had T-Case issues like the rest of you, however I have never drained anything out of the case that did not look it was brand new out of the container. I wonder what the difference is. I drained at 50K per the manual prior, but on the new case, I'm going 25K. We'll see how it works out. So far, so good.

Big2dabank · Dec 23, 2016

I agree with the T-Case diagnosis especially the chain at that mileage. I am replacing my BW 4484 t-case on my H2 this weekend with a remanufactured t-case, that way I can pull mine apart and rebuild it at my leisure to keep or maybe sell. I paid $1,500 with no core swap and free shipping which is a pretty fair deal.

5gn-h3t · Dec 23, 2016

I pulled it out and took it apart. The chain is unbelievably stretched. I'll get a measurement when I get time. Lots of fine dust on everything. The pump pickup is crushed and full of sealant and various metals. At some point it got a metal shift fork and way too much silicone sealant. Nothing is destroyed but everything is worn. I doubt I will bother fixing it. It's a 4493. It's lived a long life. Time for a new one.

Bruces · Dec 24, 2016

Anyone have a step by step on replacing the chain?

jphh20 · Dec 24, 2016

Bruces said:
Anyone have a step by step on replacing the chain?

I have not come across a step by step for the chain but it's fairly straight forward. I just did mine last month and replaced the plastic shift fork.

Here is a link to remove, split and replace the fork. I found it helpful and the case might seem to large to drop with the cross member in but it is possible. Slide it, rotate and drop it down.

Here are a few pics and notes from my chain replacement:

-make sure chain rotates smoothly before removal
-make a note where timing marks for chain and sprocket is (I took photos)
-pull up evenly on gear and planetary
-put down in same position on clean surface
-line up new chain in same order and install gear and planetary
-clean case with mineral spirits and flush fluid strainer (some have a snubber my 06' does not)
-reverse install back into case
-rotate chain multiple times and directions to check for easy rotations
-manually check shift modes for proper engagement
-seal case and install (check rotation and shift engagement on last time)
-install, fill with fluid (check your year for proper level, I had to top off through speed sensor 06').

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jphh20 · Dec 24, 2016

jphh20 said:
I have not come across a step by step for the chain but it's fairly straight forward. I just did mine last month and replaced the plastic shift fork.

Here is a link to remove, split and replace the fork. I found it helpful and the case might seem to large to drop with the cross member in but it is possible. Slide it, rotate and drop it down.

Here are a few pics and notes from my chain replacement:

-make sure chain rotates smoothly before removal
-make a note where timing marks for chain and sprocket is (I took photos)
-pull up evenly on gear and planetary
-put down in same position on clean surface
-line up new chain in same order and install gear and planetary
-clean case with mineral spirits and flush fluid strainer (some have a snubber my 06' does not)
-reverse install back into case
-rotate chain multiple times and directions to check for easy rotations
-manually check shift modes for proper engagement
-seal case and install (check rotation and shift engagement on last time)
-install, fill with fluid (check your year for proper level, I had to top off through speed sensor 06').

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Link for fork replacement:

http://www.hummer4x4offroad.com/forum/showthread.php?5365-Plastic-shift-fork

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Bruces · Dec 24, 2016

The link is helpful, thank you. Where are the timing marks that you refer to and what are you lining the up to? Also what little pin is the one that breaks easily? I have an 07 with adventure package, i believe 4494 transfer, are the chains and forks the same? Mine has 135k on it and i am sure the chain is stretched. Might as well have a fork ready so when i get in it i can replace if not already done.

4speedfunk · Dec 24, 2016

Chains & forks are all the same. The chain has a blue link that must be on the topside (shown in the photo). The sun and planetary gears have timing marks that must be aligned with each other. The small pin you've heard about is on the end of the shift fork rod. It can easily snap off. All it does is hold the rod in place until you get both halves of the case bolted together. You can still use the rod with the tip broke off...but it will be a total PITA to reassemble. Don't forget to clean the magnet while you have it apart....for the life of me I don't know why GM did not use a magnetic drain plug...you must disassemble it to clean the magnet. Lastly, the cases are magnesium (not aluminum) and this will react with steel, so you must use RTV on the case bolts, the mating surface, and also where the encoder bolts up.

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Bruces · Dec 24, 2016

Thanks for all of the info

4speedfunk · Dec 25, 2016

Download this from Schwarttzy and study it. The real meat starts at page 100. Page 194 shows the timing mark alignment for the sun & planetary gears. There are no marks for the chain, it simply has the blue link to tell you which side faces up. If you install a new chain, you just slap it in. However if you plan to re-use a previously installed chain, you need to mark it (and the pulleys) to get it reassembled in the same orientation.
http://schwarttzy.com/wp-content/uploads/2013/01/Hummer-H3-Transfer-Case-1.pdf
The sun & planetary gear timing is critical, and you need to spend some time cycling thru the modes on a workbench, to make sure it's not binding. Don't think to yourself..."it's just tight because the chain is new". If there is binding...its probably misaligned timing marks. I use some channel lock pliers to run the case thru all modes on the bench. Spin the input while doing this and make sure it's smooth and engages each mode. 4LO-locked is easy to find but 4Hi-locked can be hard to differentiate from 4Hi street. You should be able to "feel" the variable slip between outputs in 4Hi-street mode. Once you are 100% sure you have all three modes working properly...install it back under the truck. Leave the encoder off until you get the t-case bolted up...it's much easier to lift and twist the case into position without it.

Bruces · Dec 25, 2016

Yeah i will definately replace the chain. Looking at the PDF it appears there are two forks. Is it just the one that is plastic and tends to wear out?

how do you switch between modes while on the bench?

4speedfunk · Dec 25, 2016

One fork is Hi/Lo, and one is locked/street. Can't recall which one is the plastic...think it is the Hi/Lo.
You can use channel lock pliers to rotate the shift shaft.

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Bruces · Dec 26, 2016

Thank you again. I will be ordering parts soon. I may order a shift shaft just in case....

4speedfunk · Dec 26, 2016

No problem, Bruces. Given the mileage, I would recommend these parts for sure...

A rebuild kit (comes with the tranny-to-tcase gasket that you will need)...
http://www.ebay.com/itm/371104135863?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

A chain...
http://www.ebay.com/itm/Transfer-Ca...9856b9c&pid=100005&rk=2&rkt=6&sd=371104135863

A shift fork...
http://www.ebay.com/itm/Transfer-Ca...ash=item1c58738315:g:lR4AAOSwMmBV3tYN&vxp=mtr

Once you get it apart, you may also want to replace the snubber (if it has one), the shift fork shaft, and the fluid pump pickup screen (often clogged with metallic debris).

Bruces · Jan 28, 2017

I tried the bearing kit and the part numbers say they are not compatible for the adventure model with the 4494 transfer. I have not found any on eBay. Anyone know a good source for rebuild kit for the 4494?

5gn-h3t · Jan 29, 2017

Bruces said:
I tried the bearing kit and the part numbers say they are not compatible for the adventure model with the 4494 transfer. I have not found any on eBay. Anyone know a good source for rebuild kit for the 4494?

I got my parts from here. Was actually a couple bucks cheaper than eBay.

http://www.americanpowertrainwarehouse.com/bw4493-bw4494/

5gn-h3t · Jan 29, 2017

I was all gung-ho to buy a new adventure model transfer case but the price has gone up yet again since the last time I checked, so...

Bad Noises, T-Case?

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