Vibrations. Stumped for now.

[ReaperHWK]

2015 Tahoe LTZ. Has vibrations when driving and almost feels to me like a misfire. Started about a month ago and is getting progressively more severe. Vibrations are not in the steering wheel feels like engine or drivetrain to me. So whatever is breaking is breaking more lol. The vibes seems to be at lower speeds around 40mph and go away at high speeds. Also when on part throttle the car vibes. Things checked/done:

1) tires were road force balanced about a year ago. I don’t see how these could be the problem. Rotated tires anyway to see if the vibes changed but stayed the same.
2) thought it could be something in front suspension. Checked all bushings they look good.
3) truck has all new magride shocks replaced about a year ago. Can’t see them being a problem.
4) went under truck and checked the rear driveshaft. Shock it all different ways seems to be good. No play.
5) noticed the front driveshaft turns in 2wd. Internet says it shouldn’t. Looks to be unrelated problem?
6) hooked up scanner and checked for misfires. Driving around I’ll get a few counts on cylinders 5,7,8. All other stay at zero. Not enough misfired to set a check engine.
7) car randomly throws a p0175 code. Bank2 rich. Replaced both pre-cat O2 sensors and the code still comes back every few days. Related?

Other things to note. The car had all new plugs in 2022. Also in 2022 I replaced all the passenger side fuel injectors(bank 2).

Anyone have any ideas? I’m just going to troubleshoot more on my own but if someone has a suggestion I’m all ears.

 

[Marky Dissod]

Did not mention what gear you were in when these vibes occur.
If you do not know what gear you are in, can you manually choose the gear to be in, maybe rule out some gears?

 

[Fless]

Use a good bi-directional scanner to view individual cylinder misfires, to either confirm or rule out the misfire thought.

What about torque converter issues?

 

[ReaperHWK]

Did not mention what gear you were in when these vibes occur.
If you do not know what gear you are in, can you manually choose the gear to be in, maybe rule out some gears?

Didn’t think of that. I’ll check it out.

 

[ReaperHWK]

Use a good bi-directional scanner to view individual cylinder misfires, to either confirm or rule out the misfire thought.

What about torque converter issues?

See #6 in the original post. 5,7 and 8 have very few misfires. I may replace the plugs and wires though to eliminat those as problems.

Not sure how I can test the torque converter but I’ll read up on it. Watched a video on it, could be the problem? I want to eliminate most other things before I point at the tranny. I’d have to bring it to a shop for that service.

 

[Marky Dissod]

Did not mention what gear you were in when these vibes occur.
If you do not know what gear you are in, can you manually choose the gear to be in, maybe rule out some gears?

Didn’t think of that. I’ll check it out.

Not sure how I can test the torque converter but I’ll read up on it.

If you (can) shift manually, notethat the only chance of the torque converter clutch locking up is when your foot is gentle enough for long enough.
If the vibes go away when you apply enough throttle to unlock the TCC, and come back after light throttle for a bit, it's likely the TCC.

 

[Joseph Garcia]

I'm with @Fless and @Marky Dissod. My first thought was the beginning of a torque converter failure.

Get it checked out, before it grenades and takes out your transmission, as well.

 

[ReaperHWK]

I'm with @Fless and @Marky Dissod. My first thought was the beginning of a torque converter failure.

Get it checked out, before it grenades and takes out your transmission, as well.

I’m leaving that way as well. I was messing around shifting manually and it seems like if I’m above 2k rpms the vibes really aren’t there. Only under low rpm and when I apply throttle.

If drive the truck in tow mode where it keeps the rpm’s up it drives better.

I’ll take it to a tranny shop.

But this also feels like it could be a low rpm misfires as they also feel similar. My scanner isn’t showing anything significant on the live data and I’m sure the check engine would go off with misfires that significant.

So yeah if I had to put money on it for now I’m going tranny like you guys.

 

[Dirty looks]

I would be looking hard at the misfire problem.

 

[ReaperHWK]

I logged today several times with my scanner that does live data and history of misfires. There is no significant misfires I am getting at all. Maybe a total count of 4.

I am going to start another thread on the torque converter; I logged some data on that and want to see what I'm looking at. I think it's the converter?

Torque converter data, trans experts inside!

So my truck is vibrating, checked a ton of stuff including misfire data and they all look OK. Nothing significant on that end. See thread: https://www.tahoeyukonforum.com/threads/vibrations-stumped-for-now.156877/ I logged some torque converter data and wondering if this is normal. I logged...

www.tahoeyukonforum.com

 

[Geotrash]

I logged today several times with my scanner that does live data and history of misfires. There is no significant misfires I am getting at all. Maybe a total count of 4.

I am going to start another thread on the torque converter; I logged some data on that and want to see what I'm looking at. I think it's the converter?

Torque converter data, trans experts inside!

So my truck is vibrating, checked a ton of stuff including misfire data and they all look OK. Nothing significant on that end. See thread: https://www.tahoeyukonforum.com/threads/vibrations-stumped-for-now.156877/ I logged some torque converter data and wondering if this is normal. I logged...

www.tahoeyukonforum.com

That's way too much slip, I agree. I forget what my numbers were after my TC replacement back in 2021 but it was very close to the commanded number. Time to get that thing out of there before it sends shrapnel through the transmission and coolers.

I replaced my 6L80 converter with a BU60FHD, which are now made by VEGE. It's a reman OEM unit with a billet cover, flanged hub, and stronger lockup clutch. Since replacing, I've towed 7500 lbs probably 30K miles with no issues. It has a more enjoyable feel than the stock converter because the uptake is strong off idle.

VEGE Torque Converters TQBU60FHD VEGE Remanufactured Torque Converters | Summit Racing

Free Shipping - VEGE Remanufactured Torque Converters with qualifying orders of $109. Shop Torque Converters at Summit Racing.

www.summitracing.com

 

[Dirty looks]

I logged today several times with my scanner that does live data and history of misfires. There is no significant misfires I am getting at all. Maybe a total count of 4.

I am going to start another thread on the torque converter; I logged some data on that and want to see what I'm looking at. I think it's the converter?

Torque converter data, trans experts inside!

So my truck is vibrating, checked a ton of stuff including misfire data and they all look OK. Nothing significant on that end. See thread: https://www.tahoeyukonforum.com/threads/vibrations-stumped-for-now.156877/ I logged some torque converter data and wondering if this is normal. I logged...

www.tahoeyukonforum.com

If your O2 sensor on that bank is a little lazy it won't be very accurate at catching misfire.
The fact that it's showing any at all is a strong indication that it's much worse than you think.

 

[ReaperHWK]

I would be looking hard at the misfire problem.

If your O2 sensor on that bank is a little lazy it won't be very accurate at catching misfire.
The fact that it's showing any at all is a strong indication that it's much worse than you think.

Both 02 sensors were replaced 2 weeks ago.

 

[Dirty looks]

If everything is right with the ignition system it shouldn't be showing misfires at all. The other bank isn't showing them.
I've been down this road . One bad coil and one bad wire. It may be your converter but the symptoms you've described have ignition written all over them.
Good luck.

 

[Dirty looks]

If everything is right with the ignition system it shouldn't be showing misfires at all. The other bank isn't showing them.
I've been down this road . One bad coil and one bad wire. It may be your converter but the symptoms you've described have ignition written all over them.
Good luck.

Out of curiosity I have to ask, why were the O2 sensors replaced? You know these trucks have six of them. One in each manifold and two in each down pipe.

 

[snives]

It's hard to say from your description, but nevertheless I must ask the question: Are you familiar with the term AFM/DoD ? During cruise conditions active fuel management will opportunistically revert to 4 cylinder operation for economy. This can be shown in the DIC and will appear as a "V4" as opposed to "V8". The vehicle will feel vibrate more and will feel like a misfire but will not register it as such since it is the intended behavior.