TCC Slip Speed or Torque Convertor Issue? (SOLVED, Drive Shaft Pinion Angle)

gmartin1215 · Apr 14, 2026

I have been hearing some rumbling from my transmission area while in overdrive, audible above 50mph, and when I de-accelerate. I thought it might have been the driveshaft, but I had the u-joints replaced and had it balanced. After more research, there is a possibility that the noise is coming from the torque converter.

I hooked up my Autel MK900BT and did live data on the TCC slip speed, and also selected the engine speed. I am seeing the TCC slip jump all over. I am new to looking at this information, so I am not sure if I am seeing an issue. It could be that the TC is not fully locked when accelerating, which might explain why I see high rpm in the TCC Slip speed. I am not sure.

I did upload a video of my live data charts. Can you all please have a look and let me know if you see anything that may indicate a bad TC?

Foggy · Apr 14, 2026

Normal Slip is about 20-40 rpms diff over engine speed. It was hard for my eyes to
see exactly the number on your graphs...
Slip 'can' be more depending on driving circumstances.
If your Torque Converter is original, It's lived its life for sure...
Usually your trans temps will go higher (than in the past) when your converter
starts slipping

swathdiver · Apr 15, 2026

Looks normal. When I'm cruising on the highway at about 70mph with the cruise on, the slip speed is only about 10-15 rpms on my three trucks.

gmartin1215 · Apr 15, 2026

Foggy said:
Normal Slip is about 20-40 rpms diff over engine speed. It was hard for my eyes to
see exactly the number on your graphs...
Slip 'can' be more depending on driving circumstances.
If your Torque Converter is original, It's lived its life for sure...
Usually your trans temps will go higher (than in the past) when your converter
starts slipping

The TC is the original with 160K on it. I know it's only a matter of time, but I was wondering if the rumbling I am hearing in overdrive is coming from the TC. It could be it, or something else. But I was hoping the TCC slip speed rmp would indicate something. I can post another vid just showing the numbers over the graph. I'll see if there are other PIDs to map from my meter, too, like duty cycle, but I think that was missing

gmartin1215 · Apr 15, 2026

swathdiver said:
Looks normal. When I'm cruising on the highway at about 70mph with the cruise on, the slip speed is only about 10-15 rpms on my three trucks.

OK, thanks.
So when the TCC slip speed is like up in the hundreds, then what is it doing? Just partially locking?
Just trying to understand this more.

LSCALADE · Apr 15, 2026

When you are driving in overdrive lets say steady state highway speed say 70mph and you are holding around the 10-30rpm slip consistently and you encounter a hill where the load on the clutch exceeds the ability for the clutch material to grab and all of a sudden you have a major slipping occurring, sometimes in the order of 100-300rpm and it spikes up and down. Thats the situation where the trans cal cant figure out what to do with it or is in may ways limited since its trying to juggle between slipping and not slipping.

one thing you can do now at this poitn before you destroy the TCC is get someone with HP Tuners, go in there increase the Offset Pressure which is set to 26psi from factory, bump it to 35psi and go see how it drives. You should swap out the fluid as well before doing that.
The GAIN if you are running at 0.375 bump that to 0.5. If you are on OS that has GaIn of 1.5 reduce that to 1.0. Those gain functions control how fast the systme is allowed to react to the spikes it sees in the trans.

Last thing to do is disable the DOD and remove slip from the tables for TCC Apply. All those things will correct the shudder sensation that you are feeling.
I spent an entire year learning, tuning, trying, logging, basically everything to do with TCC and shudder. My escalade needs a new TCC but thorugh tunnign I made it work with whatever material is left without slipping thus extending its life before it needs to be changed out.

gmartin1215 · Apr 15, 2026

LSCALADE said:
When you are driving in overdrive lets say steady state highway speed say 70mph and you are holding around the 10-30rpm slip consistently and you encounter a hill where the load on the clutch exceeds the ability for the clutch material to grab and all of a sudden you have a major slipping occurring, sometimes in the order of 100-300rpm and it spikes up and down. Thats the situation where the trans cal cant figure out what to do with it or is in may ways limited since its trying to juggle between slipping and not slipping.

one thing you can do now at this poitn before you destroy the TCC is get someone with HP Tuners, go in there increase the Offset Pressure which is set to 26psi from factory, bump it to 35psi and go see how it drives. You should swap out the fluid as well before doing that.
The GAIN if you are running at 0.375 bump that to 0.5. If you are on OS that has GaIn of 1.5 reduce that to 1.0. Those gain functions control how fast the systme is allowed to react to the spikes it sees in the trans.

Last thing to do is disable the DOD and remove slip from the tables for TCC Apply. All those things will correct the shudder sensation that you are feeling.
I spent an entire year learning, tuning, trying, logging, basically everything to do with TCC and shudder. My escalade needs a new TCC but thorugh tunnign I made it work with whatever material is left without slipping thus extending its life before it needs to be changed out.

Justin at Blackbear tuned the TCC slip by reducing the target to zero, or near zero. I am unsure how that fits with what you are suggesting, if at all.

Anyway, I want to see if this rumbling I am hearing is related to TC, and how much time it may have left. I'll see if I can find an HP Tuners device to play with those parameters, and see if that rumbling goes away. I might just bite the bullet, too, and pay a tranny shop for a diagnostic. Not sure how flashing from this device will affect other tuning done by Justin.

Obviously, the last thing I want is for something catastrophic to happen and for me to be broken down along the side of a highway, or worse, in the wilderness. But if there is anything indicating a potential problem, then I want to get on that sooner.

Are there any other PIDs I should scan to see if the TC is on its way out?

swathdiver · Apr 16, 2026

gmartin1215 said:
OK, thanks.
So when the TCC slip speed is like up in the hundreds, then what is it doing? Just partially locking?
Just trying to understand this more.

Yeah, it locks and unlocks all the time as conditions dictate. Mine has looked like yours for years and runs fine.

gmartin1215 · Apr 17, 2026

swathdiver said:
Yeah, it locks and unlocks all the time as conditions dictate. Mine has looked like yours for years and runs fine.

OK, cool. I was hoping that is the case. Good to know this part of the TC is behaving as expected.

How many miles on yours, and does it still have the original TC?

I have 160K on mine with the original TC.

swathdiver · Apr 17, 2026

gmartin1215 said:
OK, cool. I was hoping that is the case. Good to know this part of the TC is behaving as expected.

How many miles on yours, and does it still have the original TC?

I have 160K on mine with the original TC.

Just turned 223K and the transmission and converter are original.

mikez71 · Apr 17, 2026

239k here, original from what I can tell..

gmartin1215 · Apr 17, 2026

Good to hear you guys are getting those miles from out these trannies and TCs!

Mine has been mostly good. Couple of hiccups, but I think that was mostly from low fluid the time it happened.
I do tow with mine occasionally, while going over mountain passes, so have been stressing it out. The last time I towed up a steep pass, it would not shift out of 2nd until I pulled over and stopped, but it drove normal after that. It could be I was just heavy, and that was the gear it could stay at with my load.

I haven't been super-religious about changing fluids, but did get changed at about 130K. The fluid looks clean and normal on the dip stick when I checked it the other day.

I also have been running an external trans cooler since about 130k since I would get up over the 200 degree mark when towing up passes.

If I can narrow down where this rumbling sound is coming from in the transmission/transfer-case area, then I can work towards getting that fixed.

My hunch was that it might be the TC since I have heard these give out. I am going to do a stall speed test later today to see if that may indicate anything. If that looks normal, then I'll likely take to a shop and see if they can narrow it down further.

I started hearing this noise after I did the re-gearing in the diffs, but I did also got both driveshaft u-joints replaced and both balanced. It could be that sound was always there, but with the new and tighter u-joints the sound is more pronounced. I thought it could also be the new diffs and LSD, but had that work checked too. So, leads me to believe I may have some worn parts/gears in my tranny or transfer case.

Part of me thinks I mak be going down a rabbit-hole here, but the other part of me is saying I have a 160K on this tranny and I should do something about it before it breaks down on the side of the road, especially if I tow. However, transmission work is going to be big $$$$ and I already spent a big $$$$ on re-gearing.

I'll keep digging and let you all know what I find out. If you have suggestions for other things to tes, then please let me know.

gmartin1215 · Apr 18, 2026

Tested out my TC stall speed, and I got about 1700-1750 rpm at WOT in D and R (parking and foot brake applied, and wheels chocked).

Trying to look up what the normal range is, and I got answers that said typically the factory stall speed is 1800-2000 rpm

So it seems I am low on that TC and potentially need to change it out.

Also, I had someone ride with me to help pinpoint the rumble sound when I take my foot off the gas and the transmission is in 5th or 6th. I had the person sit in the second row seats and he said he could feel it more where he was sitting rather than more forward where the transmission and transfer case are. So, this sound may be coming from the main drive shaft. That shaft is steel and did get balanced when I got the u joints chnaged.

Anyway, if the stall speed I gave indicates anything to you, then please let me know.

Marky Dissod · Apr 19, 2026

gmartin1215 said:
Tested out my TC stall speed, and I got about 1700-1750RpM at WOT in D and R (parking and foot brake applied, and wheels chocked).
Trying to look up what the normal range is, and I got answers that said typically the factory stall speed is 1800-2000RpM
So it seems I am low on that TC and potentially need to change it out.

Brake check stall speed is typically slightly lower than what GM OE cites as the stall speed; you simply measure it differently than GM OE does.
Your results would be pretty close to what others would find if they performed the same test.

If you're nonetheless considering a torque converter upgrade, you need a conversation with FTI / Yank / Circle D / Ultimate / Vigilante, or a similarly reputable firm.
*It is possible to find a torque converter with 'tighter' throttle response AND a higher stall speed, it'd be costly, and it'd be well worth the premium.
*It's more likely to find a torque converter with typically looser throttle response and a higher stall speed, regardless of price it'd be a mistake since you tow.
*Normal people who tow and don't want to spend extra get a torque converter with 'tighter' throttle response and a lower stall speed. Wiser, but less fun.

You really ought to reread and thoroughly consider @LSCALADE's tuning advice. I'd implement it to see if it helps, which it likely would.

gmartin1215 said:
Not sure how flashing from this device will affect other tuning done by Justin.

Justin already has the same 'files' that were uploaded to your ecm and tcm. You ought to read them out yself from the vehicle so you won't need to bother Justin,
so you'll have Justin's 'OE' file. (I'm calling his file OE because you ought to think of it that way, as replacing GM's inferior OE file.)
That will let you revert to it after making any changes, such as the changes LSCALADE advised.

gmartin1215 said:
I was wondering if the rumbling I am hearing in overdrive is coming from the TC.

To remind everyone else, 5th & 6th are the 6L80's overdrives. If you don't hear / feel anything in 1/2/3/4, then the torque converter CLUTCH is likely the issue.
You could also try temporarily tuning out the TCC in 5th & 6th to see if the sensations change.

Engine Half@$$ is disabled, right? What I'm wondering is if the torque converter clutch changes that go with those changes were also implemented concurrently.

Long story short, GM uses TCC slip to mask noises / vibrations / harshness (NVH - GM have a very low opinion of normal people's understandings of NVH).
For a small increase in NVH (mostly from slightly higher line pressures), the TCC, the TC, and the transmission can last longer, or withstand more abuse, or both.
To oversimplify, driver and riders would 'clearly notice' each shift and every torque converter clutch engagement and release by feel,
instead of slowly wearing out the TCC to hide each transition.

gmartin1215 · Apr 19, 2026

Marky Dissod said:
Brake check stall speed is typically slightly lower than what GM OE cites as the stall speed; you simply measure it differently than GM OE does.
Your results would be pretty close to what others would find if they performed the same test.

If you're nonetheless considering a torque converter upgrade, you need a conversation with FTI / Yank / Circle D / Ultimate / Vigilante, or a similarly reputable firm.
*It is possible to find a torque converter with 'tighter' throttle response AND a higher stall speed, it'd be costly, and it'd be well worth the premium.
*It's more likely to find a torque converter with typically looser throttle response and a higher stall speed, regardless of price it'd be a mistake since you tow.
*Normal people who tow and don't want to spend extra get a torque converter with 'tighter' throttle response and a lower stall speed. Wiser, but less fun.

You really ought to reread and thoroughly consider @LSCALADE's tuning advice. I'd implement it to see if it helps, which it likely would.

Justin already has the same 'files' that were uploaded to your ecm and tcm. You ought to read them out yself from the vehicle so you won't need to bother Justin,
so you'll have Justin's 'OE' file. (I'm calling his file OE because you ought to think of it that way, as replacing GM's inferior OE file.)
That will let you revert to it after making any changes, such as the changes LSCALADE advised.

To remind everyone else, 5th & 6th are the 6L80's overdrives. If you don't hear / feel anything in 1/2/3/4, then the torque converter CLUTCH is likely the issue.
You could also try temporarily tuning out the TCC in 5th & 6th to see if the sensations change.

Engine Half@$$ is disabled, right? What I'm wondering is if the torque converter clutch changes that go with those changes were also implemented concurrently.

Long story short, GM uses TCC slip to mask noises / vibrations / harshness (NVH - GM have a very low opinion of normal people's understandings of NVH).
For a small increase in NVH (mostly from slightly higher line pressures), the TCC, the TC, and the transmission can last longer, or withstand more abuse, or both.
To oversimplify, driver and riders would 'clearly notice' each shift and every torque converter clutch engagement and release by feel,
instead of slowly wearing out the TCC to hide each transition.

Thanks for this detailed response!

I do have the AFM/DoD disabled on the ECM (assuming that is what you mean by Engine Half@$$).

Is there a way to look at Justin's files? I usually just take what he gives me and upload to the truck, and then do the reverse to give him a log file. I do have the EFI Live Scan and Tune software, but I never checked if I could see the PIDs. I'll check into that.

mikez71 · Apr 19, 2026

I see stall speeds listed as 1600-1800, upto 2100 if modified with more HP..

The tradeoff to locking the TCC solid, is too much pressure can deform the stock cover, potentially causing the friction lining to break, or so I've heard..

That is not to say upping the pressure and reducing slip is not worth trying and may fix issues for many, but just another thing to consider if cranking pressures way up.

Considering you can feel AFM mode, I believe that maybe the bigger contributor to failed stock converters..

That's my inexperienced view anyway..

Since you say the rumble happens when you take your foot off the gas, it doesn't seem to me like a TCC issue.. Maybe have someone ride in the very back over the rearend?

Marky Dissod · Apr 19, 2026

gmartin1215 said:
Is there a way to look at Justin's files?

Yes, at least the files Justin used to tune your vehicle - read out your vehicle's tune files and save them.
Don't know if Justin would give you 'loose' copies to 'work with', but you're driving the 1st copy right now.

If you use HPT to download, you'll wind up with a .hpt file (which is actually a combo of the ecm file & tcm file, I think).
If you use EFILive to dload, don't know if you'll wind up with one or two files, but your concern is the (MOSTLY) tcm behavior anyway.

Engine Half@$$ is a major contributor to TCC wear because it uses the TCC slip margins GM intended (to mask NVH) more often,
but even though disabling Engine Half@$$ reduces the pace of TCC wear, GM's TCC slippage allowance is the root cause that needs addressing.

gmartin1215 · Apr 21, 2026

mikez71 said:
I see stall speeds listed as 1600-1800, upto 2100 if modified with more HP..

The tradeoff to locking the TCC solid, is too much pressure can deform the stock cover, potentially causing the friction lining to break, or so I've heard..

That is not to say upping the pressure and reducing slip is not worth trying and may fix issues for many, but just another thing to consider if cranking pressures way up.

Considering you can feel AFM mode, I believe that maybe the bigger contributor to failed stock converters..

That's my inexperienced view anyway..

Since you say the rumble happens when you take your foot off the gas, it doesn't seem to me like a TCC issue.. Maybe have someone ride in the very back over the rearend?

I rode in the back while having my son drive around, and put my ear to the floor. I am hearing that problematic niose coming from the rear diff (like a high-pitched rumbling/buzzing ringing). When I am driving, almost seemed like the noise was coming from transfer/transmission area.
Anyway, I am taking the truck back to the diff shop next week to have them evaluate the rear to make sure all there is good. At least, remove this variable. If all good there, then I will take the truck to a reputable 4x4 shop to have them see if they can determine the cause for the noise (could be pinion angle is causing the vibration/noise - I'll do my own checks here, but they may be able to better dial it in). The reason I'll do this step is that the diff guy knows diffs, but when it comes to lifted 4x4s, he admits that he is not an expert at eliminating driveline NVH.
If all good here, then I'll go back to exploring if it is the TC and/or transmission. But what I have tested so far seems to indicate I am OK here, except for the high mileage on the unit. I am due to have the transmission serviced, so probably will be a good time to take it to a shop and have them do a full diagnosis to see if they indicate anything that needs attention.

Ugh! I hate chasing noises, but at least learning what it needs and doen't need along the way.

As always, I appreciate all the tips/advice provided by this group!

gmartin1215 · Apr 21, 2026

Marky Dissod said:
Yes, at least the files Justin used to tune your vehicle - read out your vehicle's tune files and save them.
Don't know if Justin would give you 'loose' copies to 'work with', but you're driving the 1st copy right now.

If you use HPT to download, you'll wind up with a .hpt file (which is actually a combo of the ecm file & tcm file, I think).
If you use EFILive to dload, don't know if you'll wind up with one or two files, but your concern is the (MOSTLY) tcm behavior anyway.

Engine Half@$$ is a major contributor to TCC wear because it uses the TCC slip margins GM intended (to mask NVH) more often,
but even though disabling Engine Half@$$ reduces the pace of TCC wear, GM's TCC slippage allowance is the root cause that needs addressing.

I did talk with the guy that answers the phone at BBT and he said I'll need a different version of the software I have for reading all the tune files (I lust have EFI Live Scan and Tune). I don't have HPT. But I'll fetch a file from my AutoCal and see what I can do with it, and check with EFI to see what other utilities they may have.

swathdiver · Apr 21, 2026

gmartin1215 said:
Tested out my TC stall speed, and I got about 1700-1750 rpm at WOT in D and R (parking and foot brake applied, and wheels chocked).

Trying to look up what the normal range is, and I got answers that said typically the factory stall speed is 1800-2000 rpm

The more horsepower in front of a torque converter, the higher it will stall. Mine is about that, the 6.2 Sierras stall a few hundred rpms higher with the same converter.

TCC Slip Speed or Torque Convertor Issue? (SOLVED, Drive Shaft Pinion Angle)

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