TCC questions/problems

[dexterous]

So I get the P0741 code upon acceleration. I have EFIlive V2, so I can see that is in fact slipping. I found if I let up on the accelerator at full duty cycle it locks up just fine and doesn't throw the code. I only throws the code if I don't let up on the pedal.

Once it locks, its a good lock and never slips more than a couple RPM. Here's another weird thing though. It doesn't unlock if I apply the brakes, and it doesn't unlock when it does a downshift to fourth at WOT. Aren't both of those supposed to create a short unlock period?

And lastly, there is a whining noise when I first start the truck and put it into gear and have the brakes applied. The noise is non existent in park or neutral. And the noise goes away when I let off the brakes.

Could anyone help point me in the right direction to diagnose this? Thank you in advance for any help you can give.

 

[Mike L.]

So I get the P0741 code upon acceleration. I have EFIlive V2, so I can see that is in fact slipping. I found if I let up on the accelerator at full duty cycle it locks up just fine and doesn't throw the code. I only throws the code if I don't let up on the pedal.

Once it locks, its a good lock and never slips more than a couple RPM. Here's another weird thing though. It doesn't unlock if I apply the brakes, and it doesn't unlock when it does a downshift to fourth at WOT. Aren't both of those supposed to create a short unlock period?

And lastly, there is a whining noise when I first start the truck and put it into gear and have the brakes applied. The noise is non existent in park or neutral. And the noise goes away when I let off the brakes.

Could anyone help point me in the right direction to diagnose this? Thank you in advance for any help you can give.

If as in your signature you have a transplant; who knows. P0741 indicates the converter never locked. If it actually locks on lift throttle I would suspect a bad converter, broken sealing ring on stator support, or some weird electrical problem. I would hook up a Tech 2 and watch the command for TCC.

 

[dexterous]

If as in your signature you have a transplant; who knows. P0741 indicates the converter never locked. If it actually locks on lift throttle I would suspect a bad converter, broken sealing ring on stator support, or some weird electrical problem. I would hook up a Tech 2 and watch the command for TCC.

Thanks Mike for confirming my worries haha. Guess I'll have to find a tech 2. The efilive data log showed my commanded duty cycle percentage of 65.5, but does a tech 2 give more info? It's gonna be a double pain if it's the converter. It's a brand new Hughes converter and on top of that those duramax transplants are tight to get the tranny out

 

[Mike L.]

You need to override the TCM and try commanding TCC manually. You can do this with a Tech 2. Don't know if EFI can do it.

 

[mike diesel]

You should be able to do it with EFI live. The VCS function, I think that's what it is called, and select the tcm, then you can command the tcc on.

 

[duratothemax]

You should be able to do it with EFI live. The VCS function, I think that's what it is called, and select the tcm, then you can command the tcc on.

DVT's

 

[mike diesel]

There we go, DVT function!

 

[dexterous]

Thanks guys, yeah I went into the DVT tab the other day and did the override. It behaved the same way. I held a constant 37 mph, was in 5th gear, and I engaged the clutch with efilive. Same thing happens, slipping. I let up on the throttle, slipping went away and got a solid lock with no slip. I'm taking it too an Allison service center tomorrow. The tech there said with a triple disc converter you need more pressure on the clutch. I've never heard that about the 6 speed?

 

[Mike L.]

Thanks guys, yeah I went into the DVT tab the other day and did the override. It behaved the same way. I held a constant 37 mph, was in 5th gear, and I engaged the clutch with efilive. Same thing happens, slipping. I let up on the throttle, slipping went away and got a solid lock with no slip. I'm taking it too an Allison service center tomorrow. The tech there said with a triple disc converter you need more pressure on the clutch. I've never heard that about the 6 speed?

The Allison tech is wet behind the ears. The same piston is used in the 3 disc converter. The cover is billet and they made room for 2 additional clutches.
I would almost bet that the converter builder used Sonnax components. They never work worth a shit.

 

[dexterous]

The Allison tech is wet behind the ears. The same piston is used in the 3 disc converter. The cover is billet and they made room for 2 additional clutches.
I would almost bet that the converter builder used Sonnax components. They never work worth a shit.

Well based on your wisdom Mike, guess I'll pull out the triple disc and put the original back in this weekend and see if that makes a difference.

 

[Mike L.]

Well based on your wisdom Mike, guess I'll pull out the triple disc and put the original back in this weekend and see if that makes a difference.

Before you shit can the converter, check and make sure the 2 sealing rings are ok on the stator shaft. If they're not; there's your problem. I would also check the 2 sealing rings on the input shaft. That will require bell housing removal. Worth the extra effort.