2015 Chevy Tahoe Transfer case issues

[ChevyTahoeSkier]

We have a 2015 Chevy Tahoe with 147k miles. Transmission was replaced about 30k miles ago. Started having issues in September and took it in. They replaced the Torque converter. Had it back about a month and similar issues, a noticeable lag between shifting lower gears when it is in Auto, but not when in 2wd. Brought it back, and they are now saying the transfer case has gone bad. Because they were backed up when the torque converter went, they took about a month after the part came in to get it in and fix it. They claim I was fine to drive it with the torque converter being bad and that it wouldn't cause other damage. I don't know enough to know if this is right, but it all seems super shady to me. Anyone that can offer any insight would be greatly appreciated!!!

 

[Bill 1960]

Hi, we need more information.

Who replaced the trans 30k ago and with what? Obviously not a GM part or it would still be in warranty.

What were the “issues“ with the TC? Much depends on whether it was an external problem or an internal problem that can kill the transmission.

Delayed up shifts only in 4 auto? And that’s similar to the original issues, right?

And who is “they”? Dealer, transmission shop, corner garage? In other words what is their level of competence and reputation.


There are plenty of reports where a failure of the torque converter clutch sheds material that ultimately destroyed the transmission.

 

[ChevyTahoeSkier]

Bill 1960 - appreciate the reply and additional questions. As you can tell, I am swimming a bit beyond my depth. The transmission was replaced by my local Chevy dealer and so was the torque converter. I asked them about the transfer case being covered under that warranty and they said it was not related.

The lag in shift only seems to happen at low speeds and yes only when the car is accelerating (up shifts). We have almost always driven with the car in the "auto" setting (versus the 2wd or 4wd setting) as we assumed that was the correct default. From my research now, I believe that may not be the best setting for full time use on dry roads.

The dealer didn't specify what exactly is wrong with the transfer case, just that it is what is causing the problem and it is what needs to be replaced. They are supposed to be calling me back this morning with more information, I can try to ask a few follow-up questions.

 

[Oh Kee Pah]

Thank you @ChevyTahoeSkier - I am following...

Do you have a copy of the service invoice from the new transmission install that your local dealer did? That should list the actual transmission that was installed.
You may want to call the dealership and have them confirm the exact "new" transmission that they replaced your old with, as well as any particular warranty associated with that work.

 

[Bill 1960]

Something is fishy. The torque converter should have been replaced when the transmission was done. And you should have a 100k warranty on that. Did they charge you again for another torque converter in September, or was that warranty from the first repair 30k ago?

A new (if it was done) TC should last much more than 30k.

OR- if a new trans was installed with the old TC that’s incompetence.

Insofar as the current situation, there’s nothing in the transfer case to affect shift timing, unless it’s got a major malfunction causing so much internal resistance the vehicle is dragging (as if the brakes were applied). Which I would expect to be accompanied by nasty noises and total destruction in short order.

Keep it in 2H and get a second opinion.

And you DO have four identical tires on it, right? Unequal tire sizes can cause binding in 4wd vehicles, although with it in auto that shouldn’t happen. And usually it will set off an ABS code because the wheel speeds do not match.

 

[ChevyTahoeSkier]

Bill 1960 - I agree, much seems very off. There aren't really any loud noises or clunking, it's really just not shifting smoothly. We were having some trouble a while back with it binding up on tight turns and the ABS light coming on. We were far from a dealer at the time (due to COVID) and had a local garage replace the front diff mount on the one side. I'm going to pick it up this afternoon and take it to a local AAMCO and see what they have to say.

 

[Bill 1960]

Bill 1960 - I agree, much seems very off. There aren't really any loud noises or clunking, it's really just not shifting smoothly. We were having some trouble a while back with it binding up on tight turns and the ABS light coming on. We were far from a dealer at the time (due to COVID) and had a local garage replace the front diff mount on the one side. I'm going to pick it up this afternoon and take it to a local AAMCO and see what they have to say.

This is important information. If it was binding on turns in auto then the transfer case shift motor/ encoder is malfunctioning and it’s in 4H not 4A.

OR there’s a mechanical issue with the front wheel drive clutch in the transfer case.

In either case it’s remarkable that it doesn’t throw codes and turn on the warning to “service 4wd system“.

Diff mounts do go bad but the symptom of that is a clunk. Not binding or ABS faults.

You may have a cascade of issues from faulty wheel or shaft speed sensors. The transfer case control module compares the speeds of various components to determine when to engage the front drive clutch in 4A.

 

[swathdiver]

We have a 2015 Chevy Tahoe with 147k miles. Transmission was replaced about 30k miles ago. Started having issues in September and took it in. They replaced the Torque converter. Had it back about a month and similar issues, a noticeable lag between shifting lower gears when it is in Auto, but not when in 2wd. Brought it back, and they are now saying the transfer case has gone bad. Because they were backed up when the torque converter went, they took about a month after the part came in to get it in and fix it. They claim I was fine to drive it with the torque converter being bad and that it wouldn't cause other damage. I don't know enough to know if this is right, but it all seems super shady to me. Anyone that can offer any insight would be greatly appreciated!!!

Could still be a torque converter problem. It's possible the transfer case was worn out prematurely by running it in Auto all the time. A scan tool can diagnose the transfer case and adjust it internally if something is worn down but not out, same with the transmission, the GM dealership ought to know this though they do not often get technical with customers unless pressed.

Be wary of AAMCO or any type, they almost all will say to rebuild the whole thing (whatever that is) rather than fix just what is broken. Sometimes that's not a bad thing. Keep us posted.

 

[lbenson]

Transfer case has to have been killed prematurely by running it in 4A most of the time. ALWAYS ALWAYS ALWAYS run the truck in 2WD unless conditions permit for 4A (Snow... stuck in mud... etc). Otherwise dry pavement and 4A will kill the transfer case. I've heard of many stories from friends or mechanics of the transfer case being destroyed by 4A. It (the transfer case) should be running pretty normal at 147k miles. Transmission replacement doesn't surprise me, 117k seems a little early but for the 6 speeds maybe not. Had 175k on my 2015 with the 8 speed when it went out (original transfer case on that... no issues with it as was always serviced and never ran 4A on dry pavement.)