Been a while, hope everyone is doing well.

Seems like it’s Transfer Case season… so; 2009 H3 Championship Edition, 150k miles. Was in shop having front end work done (lower ball joints, axle seals), and when they finish and attempt to back out, truck won’t move. They end up having to put it in 4H (Locked) to back out of the garage. (I absolutely trust this shop, been using them for years, they always do stellar work)

Long story short; I went through shifting the t-case (4H, 4H locked, 4L locked, Neutral, and back), sure enough, had to drive home slowly in 4H locked. Tested in 4H locked: slowly roll forward and attempt shift to 4H open, hear t-case engage, and wheels keep turning *until* transmission shifts and then it freewheels. There is no noise (grind, clunk, or otherwise) when this happens. However, the engine and (what sounds like) the t-case seem to fluctuate rpm as if you’ve shifted the transmission into N. The other odd effect: speedometer will report 20-40mph during this problem (even though the truck is stationary).

While attempting to diagnose the problem, I borrowed the shop’s code reader, and the only code even remotely related was in the t-case history: U1017 (lost communication with ECM). There are no codes from the transmission, and nothing reported *during* my t-case shifting.

So…Got any ideas what’s going on? Admittedly, the transmission and t-case are probably beyond my skill/capabilities/comfort level to fix at home, but I’d like to at least run down the issue before handing it off to a transmission shop—and make sure it’s not just a “something got bumped loose” goof.

Thank you very much. Apologies if this has been covered before—I searched the forums but none of the existing threads seemed to fit exactly.

cheers

 

Does your H3 have a sun roof? If so, have you done the sunroof drain fix, and has the passenger side floor been wet?

If the T Case lost comms, you may have a poor connection to of failed Transfer Case Control Module which is mounted pretty close to the BCM behind the passenger side kick plate. You could pull the kick plate and inspect the connections and harness for water damage/corrosion at the TCCM.

However, you mentioned they replaces axle seals. Are you using OEM front half shafts? Did the shop insert the half shafts fully back into the front diff? I am assuming they did because you reported no strange noises/grinding.... but when you loose the front diff the only way to move is in 4H Lock.

The speed sensor is screwed into the T Case above the fill hole. The shop should not have been near that based upon what you say they did.

 

Thanks Doc, I knew you’d have some insight!

Yes, H3 has sunroof. No I have not performed any maintenance on the drain, however there’s been no water in the cabin. I’m in the southwest, so little chance of inundating rain. However, this vehicle lived its first decade in the Northeast, so first thing I’ll do is check the drain and any corrosion.

Just to clarify, you are talking about the interior passenger side (kick panel)?

Will update when I’ve checked your suggestions. I’m glad I have the factory service manuals…

 

That's it, correct.

 

That's helpful to know (losing front diff). I implicitly trust the mechanics there, but I'll be under the truck to make sure. Yes, OEM half-shafts.

I did forget to mention one instance of noise: when test shifting the t-case back into 4H (open) from 4H (locked), as I mentioned, it would move, but only until (it seemed) the transmission shifted or engine speed changed, then the truck just coasted as if in neutral but the speedometer was reading 20-35mph (fluctuating). At that point, I shifted the transmission into Neutral to see if that would stop the "freewheeling" effect (it did not) and then I almost reflexively shifted into park. That was when I heard grinding. Not sure if this helps narrow anything down, but wanted to mention it, in the event it narrows diagnosis.

 

One more thing (apologies, I overlooked this, being hyper focused on sudden loss of 4H open…)

Adding this just in case it's even slightly related:
Leak/seepage of fluid from the vent line at the crossmember nearest the transfer case. Definitely ATF. First noticed it approx. 40 days ago, checked trans and t-case levels (all good), so I've just been keeping an eye on it, while I waited for my scheduled appointment with the other shop I use (not the same as the front-end shop referenced in the original post). Now I am wondering if any of this whole clusterf*** is related?

There are no leaks anywhere else (visible anyway) around the transmission or transfer case. When I first ran down the source of the leak I cleaned the area to make sure it wasn't accumulating from elsewhere. It is definitely dripping from the vent line. I will also note that both transmission and t-case were drained immediately upon taking ownership, new trans filter, and filled with Amsoil synthetic (37,350 miles ago)… damn I've put some miles on her!

 

Update

Well, nothing I could try worked, so off to the local transmission shop she went. Verdict is the t-case needs to be rebuilt… Since they are gonna have it out, I'm interested in any worthy upgrades I should ask them to perform. I will continue looking through the forum to find ideas.

 

Make sure it has a Metal Shift Fork when it goes back together if it does not already have one. GM # 19180438

 

Doc, wanted to thank you again and update: rebuilt transfer case, working like a champ! Now for other issues… ugh