2018 1500 6 speed sometimes feel like I am taking off from a stop on rumble strips

[No Tyme]

As stated above sometime when I pull from a stop it feels as if I am on the edge of the road with them little rumble strips. Doesn't last long, before I hit 10 mph its gone and only does it every now and then. Had trans flush last month at GM dealer. Was told there wasn't anything noticeable...

ALSO noticed if I pull down into "L" and select gear #5 the engine stays in V8 mode... Didn't know that.

Truck has 105K and I think shocks are worn but other than that it runs straight and no other issues that I have noticed.

I am hoping its not trans or converter issue.

Ideas?

[WT35002017]

There have been so many posts on many different forums and YouTube describing how the torque converters are failing, specifically the clutch liners.  If you got over 100k miles on yours you are a lucky one.  The programming for these transmissions lets the lockup clutch have a constant slip which causes significant wear and when the lining fails it fills the transmission with particles clogging things and this can wear the pump which can lower the pressure during shifts and finally the trans will not shift right and could be destroyed.  I wish this was an isolated incident. Best to drop your trans pan and check for lining debris or worse. I wish you the best of luck, also if you start to have erratic DOD and other electronic things going on a ground connection could be loose. There are common spots that this occurs in, check out YouTube for guidance. 

[No Tyme]

2 minutes ago, WT35002017 said:

 I wish you the best of luck, also if you start to have erratic DOD and other electronic things going on a ground connection could be loose. There are common spots that this occurs in, check out YouTube for guidance. 

I was afraid of this. I do have a 90 day warranty on the trans. I think I will make a visit to the dealer and see if the warranty is any good.

[WT35002017]

I think I misunderstood the dod part of your post there. It is true, put your truck in L mode or M mode and the engine will not go into V8 mode at all. It is the cheap way to avoid using DOD. I use that function on my Caddie.

[WT35002017]

I work on my vehicles myself, I redid the programming on my truck transmission so it won’t lock until I get a new torque converter in it, maybe this fall I will have the time. My truck is out of warranty anyhow. 

[Black02Silverado]

Seems GM knows of issues but not doing much to fix it.  Like in our 2016 Suburban with the 6L80, torque converter issues all over the web. Ours went out at 82k.  I did everything to prevent it but it is a part quality issue.  Rebuild with a billet converter and Sonnax part upgrade and should be good. Along with a tune to the transmission not to lock until 6 gear.

 

Sad that manufactures don't seem to care but then as long as it makes it past warranty they are happy.

 

Oh the days of the old turbo 400. 

Edited June 22, 2022 by Black02Silverado

[No Tyme]

3 hours ago, WT35002017 said:

I think I misunderstood the dod part of your post there. It is true, put your truck in L mode or M mode and the engine will not go into V8 mode at all. It is the cheap way to avoid using DOD. I use that function on my Caddie.

I tried this out yesterday... Pulled into "L" and went up to 5th gear and in stayed in V8 mode. Once I went to 6th it would go into V4 mode. Drove 50 miles and it seemed to stay in V8 mode as long as I stayed in #5 gear.

I have the 6 speed trans, so give it a try and let me know if yours does the same.

[No Tyme]

46 minutes ago, Black02Silverado said:

Oh the days of the old turbo 400. 

I had trouble with my 14 Silverado also... the trans would rev up between 2nd and 3rd gear shift. They replaced the 3,5,R clutch drum and it shifted much better.

After that I went with a Black Bear tune for a bit more line pressure. All was good after that.

[It's Tim]

18 hours ago, No Tyme said:

 Had trans flush last month at GM dealer.

[WT35002017]

@No Tyme I did a typo there, I meant that it won’t go into v4 mode if you use L5 or L4, not L6. On my Caddie as long as I use L9 or less it avoids V4 mode. I’ve been programming GM motors using Hp tuners and there is a lot of questions as to the programability of the line pressure on the T43 TCM. It seems that even though it can be programmed, the actual line pressure will not change unless many torque related coefficients are in line to show the need for more line pressure. For any high performance application it is well recommended that a kit such as from Sonax for raising the line pressure be used. I’m personally trying it out the programming way but I will always verify line pressures with a mechanical gauge. I may switch it a built transmission in the future.

[No Tyme]

I want to clarify that when I say I want a quicker shift the ONLY reason I like the quicker shifts is that I believe the faster the shift the less wear and tear on transmission parts. Sure with a loud muffler it sounds c@@l but my reasoning is to lenghten the life of the transmission.

Am I correct in my assumption?

[Fsu11]

On 6/22/2022 at 12:55 PM, Black02Silverado said:

Seems GM knows of issues but not doing much to fix it.  Like in our 2016 Suburban with the 6L80, torque converter issues all over the web. Ours went out at 82k.  I did everything to prevent it but it is a part quality issue.  Rebuild with a billet converter and Sonnax part upgrade and should be good. Along with a tune to the transmission not to lock until 6 gear.

 

Sad that manufactures don't seem to care but then as long as it makes it past warranty they are happy.

 

Oh the days of the old turbo 400. 

What did it cost for the rebuild? and did you wait for the converter to go out or did you have it done beforehand?

[Black02Silverado]

1 hour ago, Fsu11 said:

What did it cost for the rebuild? and did you wait for the converter to go out or did you have it done beforehand?

The TC went out fast.  Driving normal, started making a sound and then within 3 miles no forward or reverse gears.  Shut down and towed it to the transmission shop.  $3,900 rebuild, new billet converter and Sonnax pump and other parts for an upgrade.  Then had Black Bear Performance tune it and not allow lock up until 5 and 6th gear.

Edited June 29, 2022 by Black02Silverado
grammer

[pokismoki]

if you lost forward or reverse gear , that's not the TC, that might of been the PR valve jammed with metal debris and you lost clutch pressure

[Ethan2k20]

Torque converter. My torque converter was failing and was the same thing while driving though. My trans has now completely failed and everythings burned up. I would advise getting it looked into and fixed asap and dont wait around for it. I need a new trans in my truck.