2000 K2500 4l80e tcc

[Mood1977]

Hello, I have a situation where when truck shifts into 4th it seems like the converter locks, unlocks, and then locks up. After that it stays locked until it is supposed to unlock again. It?s a fresh transmission by gear star. They ran it on dyno. They say it?s good and the Problem is in the truck. I am thinking about raising the lock mph to see if it helps. Any input would be appreciated.

[Jon S.]

It is difficult for people to help you, when you didn't take the time to post your current tune.

[Mood1977]

It is difficult for people to help you, when you didn't take the time to post your current tune.

The current tune is factory. I have never posted a tune before but if it is needed I will certainly do it.

[Jon S.]

Standard operating procedure on this forum - post a tune and a log.

This gets repeated hundreds of times per year.

[Mood1977]

Standard operating procedure on this forum - post a tune and a log.

This gets repeated hundreds of times per year.

I’ll get it done.

[Mood1977]

I?ll get it done.

mikecrewlog.hplmikeworkingspeedo.hpt

[Mood1977]

I have attempted to add log and tune. Not sure that it’s done correctly.

[Jon S.]

Thank you for posting your tune.

I did not realize that you were working with the old Vortec "Black Box" PCM.

Some of the OEM transmission calibrations were not great - especially the 4L80s.

Take a look at your TCC "Normal" apply / release speeds (ECM 15200). From 12% TPS to 37% TPS the third gear apply speed is greater than the fourth gear release speed. From 56% TPS to 100 % TPS the third gear apply speed is the same as the fourth gear release speed.

If you were travelling between 37 MPH and 41 MPH during the third to fourth upshift, then TCC would lock then unlock then relock.

Some operating systems will force a TCC unlock during an upshift - not certain about the old Black Box PCM - but likely.

If you look at a graphic depiction of the table, the "lines" both intersect and overlap. It is best if all of these "lines" are separate from each other - with distinct speeds.

For smoother driveability you have several options. You could setup the TCC lockup tables to only lock the TCC in fourth gear. However, your old Black Box PCM does not feature a separate table for Tow / Haul settings - you don't have a Tow / Haul "button" like the later P01 and P59 LS engine trucks featured. This means, if you adopted the above strategy, the TCC would not lockup if you were towing in third gear.

You could develop two separate tunes - one for daily use and one for towing. Whenever you wanted to tow something, you would need to flash a different tune.

Likely your best option is to never lock the TCC in second gear, and to choose a minimum speed for the third and fourth TCC lockup - perhaps around 50 MPH - so the that TCC never locks up when you are operating in town at lower speeds.

If this was the later P01 (or P59) PCM, then it would be easy to have two tunes in one - via activating Tow / Haul mode.

As you go through your tune, you will need to look at all of the TCC speeds - Normal, Economy (likely never used), Cruise, and Hot - I recommend making all of these tables the same.

This is truly a matter of driver preference - find a setup that you like, and one that will always lockup the TCC in fourth gear at highway speeds.

2000 4L80 Vortec PCM - PT TCC speeds - chart.jpg2000 4L80 Vortec PCM - PT TCC speeds - graph.jpg

[Mood1977]

Thank you for posting your tune.

I did not realize that you were working with the old Vortec "Black Box" PCM.

Some of the OEM transmission calibrations were not great - especially the 4L80s.

Take a look at your TCC "Normal" apply / release speeds (ECM 15200). From 12% TPS to 37% TPS the third gear apply speed is greater than the fourth gear release speed. From 56% TPS to 100 % TPS the third gear apply speed is the same as the fourth gear release speed.

If you were travelling between 37 MPH and 41 MPH during the third to fourth upshift, then TCC would lock then unlock then relock.

Some operating systems will force a TCC unlock during an upshift - not certain about the old Black Box PCM - but likely.

If you look at a graphic depiction of the table, the "lines" both intersect and overlap. It is best if all of these "lines" are separate from each other - with distinct speeds.

For smoother driveability you have several options. You could setup the TCC lockup tables to only lock the TCC in fourth gear. However, your old Black Box PCM does not feature a separate table for Tow / Haul settings - you don't have a Tow / Haul "button" like the later P01 and P59 LS engine trucks featured. This means, if you adopted the above strategy, the TCC would not lockup if you were towing in third gear.

You could develop two separate tunes - one for daily use and one for towing. Whenever you wanted to tow something, you would need to flash a different tune.

Likely your best option is to never lock the TCC in second gear, and to choose a minimum speed for the third and fourth TCC lockup - perhaps around 50 MPH - so the that TCC never locks up when you are operating in town at lower speeds.

If this was the later P01 (or P59) PCM, then it would be easy to have two tunes in one - via activating Tow / Haul mode.

As you go through your tune, you will need to look at all of the TCC speeds - Normal, Economy (likely never used), Cruise, and Hot - I recommend making all of these tables the same.

This is truly a matter of driver preference - find a setup that you like, and one that will always lockup the TCC in fourth gear at highway speeds.

2000 4L80 Vortec PCM - PT TCC speeds - chart.jpg2000 4L80 Vortec PCM - PT TCC speeds - graph.jpg

Thanks for the reply. Let’s say I make it not lock at all in third. When towing in 3rd, is this bad? Does the tcc need to be locked for cooling?

[Jon S.]

You will likely get varying opinions on this subject.

My two cents - as long as you are not towing, then there is no problem to only have the TCC lockup in fourth gear - and the driving experience will probably be more to your specific liking.

If you are towing something lightweight - and the 4L80 is always (or almost always) in fourth gear on the highway, then the TCC will be locked - so again, no problem.

If you need to tow something heavier, and the transmission is often running in third gear on the highway, or if you manually select third gear (to prevent an endless 3rd>4th>3rd shuffle), then the TCC should be locked in third gear - to reduce both transmission oil temperatures, and wear of the TC clutch (these were not intended to operate all day on the highway unlocked - like the older non-electronic transmission were).

[Mood1977]

You will likely get varying opinions on this subject.

My two cents - as long as you are not towing, then there is no problem to only have the TCC lockup in fourth gear - and the driving experience will probably be more to your specific liking.

If you are towing something lightweight - and the 4L80 is always (or almost always) in fourth gear on the highway, then the TCC will be locked - so again, no problem.

If you need to tow something heavier, and the transmission is often running in third gear on the highway, or if you manually select third gear (to prevent an endless 3rd>4th>3rd shuffle), then the TCC should be locked in third gear - to reduce both transmission oil temperatures, and wear of the TC clutch (these were not intended to operate all day on the highway unlocked - like the older non-electronic transmission were).

Makes sense. I think I’m going to raise the 4th lock to 50 leave the 3rd as is and see how it does. Thanks again.

[Googball]

I having the same issue but in first were do I find first
01 chevy 2500hd 6.7l 408
stock 4l80e with circle d 3200 stall