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6L80E transmission shift problem

Larsson

By Larsson
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Larsson Enthusiast

Larsson

Posted
Posted (edited)

Hi guys, I bought a 2014 chevrolet silverado 5.3 LTZ with the 6L80E transmission. When I keep the truck at a steady speed ,for example 35 m/h, the transmission keeps changing rpm. It 's constant changing between 1400 and 1200 rpm. When I drive at 50 m/h the rpm changes from 1600 to 1400 rpm. It seems that the torque converter clutch is constantly engages and disengages.

 

I allready replaced the torque converter ,flushed the transmission and reset the computer. This didn't made a difference. 

 

Does anyone have an idea? 

Edited by Larsson
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Larsson
Larsson

Here is an update on how things are going with my tcc problem.   The mechanic I took the truck to says that when he connects the diagnostic computer and pressurises the tcc the pressure drop

Larsson
Larsson

Got an E-mail back from grumpy bear's contact. He says that he machinnes the pump housing if necessary and puts in a transgo tcc kit and a transgo shiftkit. And after install he tunes the transmission

Larsson
Larsson

Hi guys,   Here's a update of how things are right now.    I tried to find someone in holland who could reprogram my transmission. After a long search I found a guy who works at th

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pokismoki Senior Enthusiast

pokismoki

Posted
Posted (edited)

did you pull the Pump and inspect the pump faces, check Techm, and replace all the valve body seals and case seals, do a low pressure air check on the case ports ? you might have seal leakage somewhere..

Edited by pokismoki
Larsson Enthusiast

Larsson

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Posted

Thanks for your reply. You give me some new things to check now.

 

Today we went on a testdrive with a diagnostic computer and the mechanic thinks it's the techm. He suspects that a bad solenoid or pressure switch is the cause. April 6th we're going to ask a tranny guy for his opinion.

Is it possible that the Pressure regulator valve has something to do with it? Or does this part has nothing to do with the torque converter?

 

When we changed the tranny fluid, it looked quite normal. There was no dirt or alu dust in the oil. So I think the oilpump is ok. The old torque converter was probably good. But you got to start somewhere and it seems like the 6L80 converters are prone to break at 100000mls. My truck just did 85000mls. 

 

 

 

 

 

pokismoki Senior Enthusiast

pokismoki

Posted
Posted (edited)

Techm has delicate pressure switches inside it, they have rebuild kits,  I would have the trans guy install all new seals and the mounting seals from the case to the pressure ports that feed the techm, if you do a low pressure test on the feed ports you might find you have a leak around the piston that puts pressure to the clutches. could be part failure due to manufactuering or the high temps GM runs the 6l80 at.  you'll know its been overheated if the seals are hard..

 

the Torque converter should last longer with a trans tune, GM over cycles the TCC  too much and this causes the wear and failure on the TC

 

 

Edited by pokismoki
  • 3 weeks later...
Larsson Enthusiast

Larsson

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Posted

Here is an update on how things are going with my tcc problem.

 

The mechanic I took the truck to says that when he connects the diagnostic computer and pressurises the tcc the pressure drops within one second or so. He said it's a faulty tehcm but I don't believe him. A transmission control module (tehcm) is quite expensive and is working or broken, at least the solenoid is. So I did something I should have done earlier. If you want something done right, you have to do it yourself.

 

So I took the tranny out again and inspected the whole thing. Replaced the pressure regulator valve with the transgo SK6L80 kit and inspected the oil pump. There was not much wear on the pump and the pressure regulator valve so I put my attension to the valvebody. 

Took the valvebody appart and put in sonnax o-ringed end plugs and a transgo 6L8CSTCC (clutch select valve and tcc regulator valve kit). 

But when I took out the tcc regulator valve the sping didn't come out. So I used a little hooked tool to get the spring out. But to my supprise the spring came out in 3 pices. I think that is the cause of my tcc issue. The tcc regulator valve was not working propperly due to a broken spring. And that's explains the pressure loss. 

 

I'm waiting for the 8 plastic checkballs to be dellivered this week and then I'm going to put it all back together and take the truck for a testdrive. 

 

I'll give you people an update on how things went.

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Dick Lichon Enthusiast

Dick Lichon

Posted
Posted

My 2014 6l80e transmission issues started at 75k miles. Made it to 109k and had to limp it into my transmission guy. He did a full billet part rebuild with all the upgrades and billet TC. Working on my 500 mile break in now. Torque converter was toast, both 2nd and 3rd clutches were burnt pretty bad. One of the drums was ready to self destruct. Pretty sad these transmissions won't make it past 100k. This truck spent most of it's miles on the highway, little towing. TVS1900 supercharger added around 105k which finished the tranny off. Mine wouldn't hold 2nd or 3rd, lots of shuddering and RPM variation while in 6th cruising around 70mph.

Larsson Enthusiast

Larsson

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Maybe I'm saying something stupid but does gm have an transmission software update to tackle this known problem? 

 

I found a video on YouTube which shows somone who has changed the transmission software with "HP tuners". (6L80E The real cause of failure and how to adress them).

 

Is it a solution to the tcc problem? 

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
31 minutes ago, Larsson said:

Maybe I'm saying something stupid but does gm have an transmission software update to tackle this known problem? 

 

I found a video on YouTube which shows somone who has changed the transmission software with "HP tuners". (6L80E The real cause of failure and how to adress them).

 

Is it a solution to the tcc problem? 

 No

 

https://www.sonnax.com/tech_resources/845-6l80-6l90-transmission-tech-advisory-consider-an-updated-converter-in-your-next-rebuild

  • Like 1
DeePa Enthusiast

DeePa

Posted
Posted (edited)

I read that article. Unfortunately mines at the dealer and I’m going with a stock one for now. Once the warranty is up on the new trans, I’ll pull it and put in a billet one. 
 

I cannot make the dealer wait for my converter to come in. I’m happy it’s covered and only costing me my deductible. 

Edited by DeePa
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
17 minutes ago, DeePa said:

I read that article. Unfortunately mines at the dealer and I’m going with a stock one for now. Once the warranty is up on the new trans, I’ll pull it and put in a billet one. 
 

I cannot make the dealer wait for my converter to come in. I’m happy it’s covered and only costing me my deductible. 

 

I understand your position and decision. I don't understand GM replacing a bad part with an identical known bad part. Especially one that will not only destroy itself but everything in the case with it.  :shakehead: This is one of those things than has gone on for quite some time and an engineered solution like they did with the oil pump and brake vacuum pump should have been implemented by now and a running change done in production. 

  • Like 1
DeePa Enthusiast

DeePa

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Posted

Agreed 100 percent. I also think the trans tuning is a big part of it. You don’t hear about the 14s and 15s having this issue. 

Larsson Enthusiast

Larsson

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I've put the valvebody in the transmission and bolted everything back in the truck. Took it for a testdrive today. Now it shifts and drives like a dream! Even in v4 mode😁. I put in a HD B85JMBX of tc remanufacturing. Lets hope that a HD torque converter last a bit longer than a stock one.

 

I'm thinking of changing the software of the transmission but I don't know somone who has the equipement to do this here in Holland. 

 

Is it duable to buy a softwareprogram and connector for myself?

  • Thanks 1
Black02Silverado Senior Enthusiast

Black02Silverado

Posted
Posted
2 hours ago, Larsson said:

I've put the valvebody in the transmission and bolted everything back in the truck. Took it for a testdrive today. Now it shifts and drives like a dream! Even in v4 mode😁. I put in a HD B85JMBX of tc remanufacturing. Lets hope that a HD torque converter last a bit longer than a stock one.

 

I'm thinking of changing the software of the transmission but I don't know somone who has the equipement to do this here in Holland. 

 

Is it duable to buy a softwareprogram and connector for myself?

You can contact Black Bear Performance.  They are a vendor on here.  They can tune the transmission.  I had them tune our 2016 Suburban and it made a huge difference.

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
4 hours ago, Black02Silverado said:

You can contact Black Bear Performance.  They are a vendor on here.  They can tune the transmission.  I had them tune our 2016 Suburban and it made a huge difference.

 

If you don't mind me asking Nick...in what way? I can't imagine mine working better that it does now but......I'm open to ideas and others results. 

Black02Silverado Senior Enthusiast

Black02Silverado

Posted
Posted
22 minutes ago, Grumpy Bear said:

 

If you don't mind me asking Nick...in what way? I can't imagine mine working better that it does now but......I'm open to ideas and others results. 

Justin was able to adjust the shift points.  It seemed to want to shift way to early and that seemed to make it feel like it didn't have power.  Now it holds the shifting a little more and is smooth.  It didn't effect the mpg's since we get 22mpg out of the big thing.

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