Torque Convertor never fully locks.

[Sqrly]

Using CarScanner I'm seeing 50rpm avg TCC slip when traveling 65 mph with the cruise control on and the vehicle fully warmed up.

I found this Trans mod post here and read through it. I watched the video and read the comments below it. Others say this mod cures the issue I am seeing. I also saw mention of PCM tuning to change the shift behavior.

Q1: I would assume the torque convertor is supposed to fully lock up at some point?

Q2: How long does it take to fully lock up? I only drove a few minutes @65 (with the cruise on).

Q3: Can this change can be done through programming? If yes how could I do that?

For the PWM on the torque converter, it lets it slip on engagement up till it eventually locks up the clutch so you don't feel it. When eliminating that PWM, either through a tune, shift kit or this mod, it will feel like a fifth gear engaging.

Note: I just recently did the trans flush and filter. I filled it with Valvoline Dex 6. I ended up using 4 gallons total.

Buying a new valve and modifying it then doing a swap wouldn't be too hard.

Q4: Why does Amazon say this ACDelco #24227792 does not fit my vehicle, but that this off brand replacement does?

Car Scanner LogFile.brc

 

[TJBaker57]

Mine goes to full lockup. However mine has been rebuilt and I have no idea what exactly was done in the rebuild. Nothing special was requested for the rebuild.

 

[TJBaker57]

20 Years Later: What’s New with 4L60-E PWM Modifications

Transmission builders are no strangers to modification. Making changes to increase performance, to prevent known issues from cropping up or to overcome existing

www.sonnax.com

 

[Mooseman]

Q4: Why does Amazon say this ACDelco #24227792 does not fit my vehicle, but that this off brand replacement does?

Because Amazon's compatibility listings suck. I checked on RA and it fits:

 

[Sqrly]

20 Years Later: What’s New with 4L60-E PWM Modifications

Transmission builders are no strangers to modification. Making changes to increase performance, to prevent known issues from cropping up or to overcome existing

www.sonnax.com

Excellent link. My TCC is working exactly as intended.

 

[Sqrly]

Because Amazon's compatibility listings suck.

Yes they do. I just wanted to triple check I wasn't missing some detail.

 

[TJBaker57]

Excellent link. My TCC is working exactly as intended.

I have long wondered if my TCC was altered in some way during the rebuild. Others here have said that theirs always has some slip where mine locks up solid.

My Yukon transmission was also rebuilt by the same shop and it also locks solid.

 

[Sqrly]

I have long wondered if my TCC was altered in some way during the rebuild. Others here have said that theirs always has some slip where mine locks up solid.

My Yukon transmission was also rebuilt by the same shop and it also locks solid.

Yours does not look correct to me. It's locking up (98%) in every gear just before shifting to the next. Shouldn't it only lockup in 4th?

I can't explain that rpm spike to 4500, did you lose traction? The math doesn't add up. A 3000 spike in RPM with only a 300 RPM slip.

 

[TJBaker57]

Yours does not look correct to me. It's locking up (98%) in every gear just before shifting to the next. Shouldn't it only lockup in 4th?

Remember what I explained about how a Tech 2 displays the TCC duty cycle? The higher the percentage the more TCC apply pressure is released. So 98% is not lockup but full release.

And I think it can also lockup in manual 3rd.

can't explain that rpm spike to 4500, did you lose traction? The math doesn't add up. A 3000 spike in RPM with only a 300 RPM slip.

There was a downshift there. From 4th with lockup down to 2nd with full TCC release.

 

[Sqrly]

Remember what I explained about how a Tech 2 displays the TCC duty cycle? The higher the percentage the more TCC apply pressure is released. So 98% is not lockup but full release.

And I think it can also lockup in manual 3rd.

Yes, I remember. I was reffering to the five 0 rpm points in the TCC Slip RPM graph. The downshift explains a few but the first one appears to happen at 20 mph.

 

[Mooseman]

Shouldn't it only lockup in 4th?

No. It can also lock up in 3rd.

 

[TJBaker57]

Yes, I remember. I was reffering to the five 0 rpm points in the TCC Slip RPM graph. The downshift explains a few but the first one appears to happen at 20 mph.

I am going to be revisiting the subject of TCC lockup and my perceptions of the reported values. Our friend @AmpOverload has contributed some findings that have me questioning my conclusions from back in June 2022 when I first experimented with this data point here in this post:

More PIDs for Torque App

In another thread there has been a handful of comments regarding Torque Pro and transmission parameters. Thought I would toss out a couple of things I wonder about here. Torque Pro has their set of extended parameters that I have long surmised initially came from user submissions. What vehicles...

gmtnation.com

As for specifics in the screenshot I posted above I think what we are seeing is the result of a great deal of latency in my data stream. You see the screenshot displays just a few of the data points I was recording. There were about 70 data points active and requesting that many PIDs can lead to each PID only getting a response every 5 seconds or so.