4L60E Torque Converter Clutch manual override

[solidaxel]

How to lock in TCC for a test, HOW TO?
I was told I could jumper pin T to pin E(Battery voltage to TCC solenoid)
at the trans plug

or at the TCM Pin 25 to Pin 32

I am guessing that it would "stay" in lock up and driving (A at any speed or
B above 45mph) "IF" the torque converter clutch and
The T/C Solenoid was 100% OK

Any other ideas as to how to command the TCC to stay on I do not have access to
EFILIVE or HPTuners

[ls1nova71]

I would think if you jump power directly to the TCC solenoid it would lock up regardless of speed, so when you try to come to a stop it would buck and kill the engine like driving a manual and not pressing the clutch when coming to a stop. That is an assumption though since they are PWM controlled so putting 12v directly to it may or may not work. Why are you wanting to test it? Generally you can feel them unlock by slightly pressing on the brake while maintaining a set speed to see if its locking or not. They use PWM to control them so you dont feel them actually lock up.

[solidaxel]

I am trying to isolate the problem!
It is not going into lockup every time the speed reaches 50mph

OK, maybe I place a switch on a 12vdc power supply and the TCC pin
and lock/unlock 50 and above If it does not go into LU
Everyone is pointing fingers at the "other" guy!
Computer......wiring.......transmission guy
I have checked and replaced 4 pin brake light switch and I placed a LED light across
the TCC power when the brake is off (light on) and the light off when brake applied
I placed a VOM (VDC) across the Transmission plug pins T & U and I see variable voltage which I presume is PWM
The upgraded trans is fresh as is the new Billett Allison LU TConverter.
I have also tried another T42 TCM with a different tune and it is doing the same thing
I have in the past been commanding a P0741 code, L/U stuck off

I thought a manual switch would isolate the trans/computer
Any Thoughts?

[YoungPup1977]

First of all, are there any codes.

I am assuming this is fresh rebuild.
Did the builder upgrade the pwm power valve. The aftermarket has designed a pwm valve to enhance the charge fill oil to the TCC. You indicated the TCC does apply but not all the time I believe. How do you know this ?
Most of the time If the TCC is not applying is would toss out a code. Maybe a 1870.

[solidaxel]

As far as I know the trans guy and his excellent builder say the fault is not their problem.
I asked him if his build would hold 500hp add yes and most likely more.
So far I have not had a problem going through the gears with the new LS3

I did have a LED on the circuit and I could see and hear the exhaust note change when it went into lock up.
The only code I have seen, and not every time is P0700 and under that is P0741

The new tune on the T42 was 50mph on and 38% throttle disengage

[YoungPup1977]

I assume you did the R&R of the transmission. That's why the fingers are being pointed.... plus tuning involved.

Take it back to the builder, I would not try trouble shooting it yourself and cause another issue to be pointed to.
Does the builder have a scan tool, hopefully it is one that can scan better than just telling, you have 700 trans codes.

Also, can you consider answering the questions I asked in post 4. Thanks.

[solidaxel]

Yes I did the R&R, and I had him install the TC into the pump and when I bolted it up there was <1/4" between the flexplate and TC and rotated freely

I asked him about the PWM power valve and a new harness and his answer was yes when we do this stage of a rebuild, we upgrade to, I think he said a "sonic"?

[YoungPup1977]

Sonnax is the aftermarket trans parts provider
Any good trans shop would try to help you out. Just take it back to them and let them figure it out. If they don’t, they aren’t as good as they say or as people think they are.
The 741 code means a difference in TC and input shaft speeds. If the difference is more than a specific rpm it will generate that code. Like I said in previous post, hope they can capture the data from a good scanner

Good luck to you !!

[solidaxel]

You seem to be convinced that the problem is in the trans and not the wiring or the computers
The trans shop only did a bench build on the trans
I am trying to isolate the problem to his trans
How would you test the TCC for lock/unlock?

[ls1nova71]

You really need to find someone with a good scanner that can command it on and off, or to watch and see what's going on. Without it you're pretty much just stabbing in the dark.

[solidaxel]

............. O K,

I will take the advice provided

I will let you know the outcome
At least he will have to prove to me the trns & TC are NOT his problems!

[Chevyrestorerman]

Have the trans expert tell you why the 741 code is being generated.

Computer is reporting a rpm difference from TC to input speeds (which means a slip)

[Chevyrestorerman]

Could be the O-ring on the input shaft. Just a thought.

[Chevyrestorerman]

I am assuming you have this type of input shaft. Notice just below the splines a grove for a O-ring. When TC was put in the front of trans the O-ring might of got nicked /cut. Just guessing, but I don’t think it’s electrical on part of the TCC solenoid.

[solidaxel]

Thanks I will quiz the builder IF he does not find the problem

[solidaxel]

I showed up at the trans shop this AM, I drove while the mechanic monitored the SnapOn scanner
He said the problem was most likely in the trans!!!!
There was enough Data for him to analyze, but he felt the problem was most likely the first code to "pop up"
which was the temp. sender in the trans was reading +300* he said he had seen them before where they were bad.
He said it may also be the torque converter "slippage" was too high >1000rpm
He felt that the wiring and TCM were OK
I left the car there too cool down and he would call me later to confirm his suspensions after he "dug" into it

He also said it could be the 'O' ring you mentioned above

More to follow!

[solidaxel]

Update.......it's fixed!!
Trans shop removed the pan and check the temp sender in the harness
and it was faulty
R&R the harness, (faulty temp sender ) filled it back up, and it is a different animal
Cross that one off the list

Thank you all for the help and suggestions

[YoungPup1977]

In post number 7 you indicated they replaced the harness so the new harness/temp sensor was bad. Interesting...

[solidaxel]

They were getting temp readings +300* and the engine was in the 200+/_

Well, with the ride home 10+ miles it stopped going into lockup above 48mph!

I then removed the brake switch circuit and placed a chassis ground toggle switch
on the purple wire from the brake switch which I think is the ground for the TCC solenoid
...... that did not work either, but with the toggle switch off/NO and on when above 48mph the TCC went in and out a few times but then stopped working

I would like to pin the purple and pink wires on the brake switch to........??
My guess is the T 42 and from there to the trans plug

Looking for a cross, open, or a transposition or even a ground,

Do you know which pin on the 49 pin connector (T42) matches the purple & pink
wires at the brake switch?

I have the TCC pins ID at the trans

Thanks for following this problem with me

[YoungPup1977]

Take it back to the trans shop, no need to be trying to troubleshoot it yourself. (as mentioned in post 6)
If you don't have a scanner and proper way of troubleshooting you are wasting your time. I bet the 741 code is still present. Take another GOOD test drive with the expert with the scan tool.
Was the TC replaced ?

What year and model of transmission / vehicle is this

[solidaxel]

The 4L60E was from a 2004 Tahoe
The trans was updated to hold 500+ hp
The T C is a billet from Allison I don't remember the numbers
The engine is a new crate LS 3
It is for one of the cars listed in my sig.

[YoungPup1977]

Waiting to see what the trans expert with the scanner says this time.
741 code most likely is still being created.

[YoungPup1977]

Any Update ?

[solidaxel]

Not corrected yet!
Added a dedicated battery circuit with a relay and switched to pin 11 on the TCM

[YoungPup1977]

Post #22 waiting for trans expert scanner results. Code 741 ??