RPM Flare After 3 - 4 Shift (4l60E)

[twenglish1]

I recently rebuilt my 4l60E and tuned with the bluecat trans tool. Lots of upgrades, Sonnax performance pack, Extreme HD performance servo, Sonnax Smart Shell, Sonnax HD Reaction Shaft, Extra Wide Red Eagle 2-4band, all new clutches, Kolene Steels, upgraded 9 clutch 3-4 pack. 2,600 RPM torque converter. Shifts beautifully, all shifts feel very quick and crisp, very happy with how it turned out. Only thing is this slight RPM flare has me concerned, when it shifts from 3 - 4, it almost feels like it locks the converter right after it shifts into 4th and releases it, RPM flares and and then it relocks the converter and it stays locked like i'd expect. This seems to happen every time the 3 - 4 shift occurs. The first 3 - 4 shift of the log shows it, roughly a 1/4 way through the log. Wondering if this is something i should be concerned about. It is installed in a 3rd gen Camaro behind a 5.3l with a BTR Truck Norris cam, TBSS intake, long tube headers and 94mm TB, axle ratio is 3.23, currently set up to run in closed loop speed density.

Current.hpt
TCC Lock.hpl

[ns158sl]

Briefly looking, need to log pedal position. Looks to be TCC looking though. 3-4 looks good in that instance.

[twenglish1]

I have throttle position on the log, unless there is a different channel I should be using for it? Looking through the log again, it almost looks like it is taking a long time to apply and the RPM flare i was seeing is it slipping until it fully engages. About halfway through the log, the 3 - 4 shift occurs again, TCC mode goes from apply en to apply, then TCC slip RPM gradually drops until TCC Mode indicates locked. Forgot to add and i will get a log of it tomorrow, i tested it with the TCC lockup speeds all set to 255 and it still seems like it does it,

[ns158sl]

Was looking at another log from a different post, sorry. Almost looks like TCC is being applied and released which doesn't jive with the tune. Only other thing I would log is any of the "shaft speeds".

[twenglish1]

Yeah that's what I thought i was seeing, couldn't seem to find any settings in the tune I had missed relating to this, I'll add the shaft speeds and record some more data

[twenglish1]

Two more logs, added the input and output shaft speed channels, was thinking if maybe this had to do with the desired shift time table, but i already have the 3 - 4 shift set to 0 across the board.


5.hpl
3.hpl

[TransGo Robert]

This one is a bit of a tricky one because those earlier 4L60E don't have an input shaft speed sensor so the value is made up by the computer. But what is happening here is that for some reason the band is releasing and sometimes just slipping some shortly after the 3-4 shift and then it grabs a bit later and then the computer commands lock-up to apply.

When it acts up it goes 3-4-3-4-lock-up. Sometimes lock-up end up applying a bit before the band finally grabs again, so I dont' think it is related to the lock-up command, it just looks like that at first. If you look at the engine RPM and the OSS RPM in those instance where it locks up before the you'll see both RPMs are the same confirming it is back in 3rd gear even though the command never changed. I don't know if there is an transmission internal issue or a command issue but you can see that the pressure command is much higher when it commands teh 3-4, then it lowers it at which point it falls back into 3rd. If you were to tune it to keep the pressure the same as it sets it during the initial 3-4 shift when it grabs it will most likely fix it. However that could be a Band-Aid covering up an internal issue, without a pressure gauge hooked to it is very hard to say.

[twenglish1]

Greatly appreciate the information, i didn't post a log of it, but i did rule out the TCC, maxed out the TCC apply table and tested, and it still does it, seems strange to me, once it shifts back into 4th after dropping to 3rd, it feels solid, haven't noticed any slipping. I haven't changed any transmission parameters relating to shift pressures. Are you familiar with this servo assembly? Put the link below. Advertises 35% more apply area than corvette servo assembly. Maybe it does need more apply pressure? I am not sure if i have any old logs with transmission channels with the old transmission but i will look, i don't recall noticing this with that transmission though.

Original transmission when i completed the swap was also a 4l60e, got really hot (probably my fault for using the internal radiator cooler with a high stall converter) and input shaft decided to "unpress" itself from the input drum and created a huge internal hydraulic leak and burning the 3 - 4, rear case lugs were all chattered up upon disassembly, so i picked up another transmission at the junkyard, disassembled, cleaned/inspected, and full rebuild with everything listed in the first post. Didn't write down all my clearances but i kept everything on the tighter end.


https://globaltransmissionparts.com/...BoCL2EQAvD_BwE

[TransGo Robert]

Greatly appreciate the information, i didn't post a log of it, but i did rule out the TCC, maxed out the TCC apply table and tested, and it still does it, seems strange to me, once it shifts back into 4th after dropping to 3rd, it feels solid, haven't noticed any slipping. I haven't changed any transmission parameters relating to shift pressures. Are you familiar with this servo assembly? Put the link below. Advertises 35% more apply area than corvette servo assembly. Maybe it does need more apply pressure? I am not sure if i have any old logs with transmission channels with the old transmission but i will look, i don't recall noticing this with that transmission though.

Original transmission when i completed the swap was also a 4l60e, got really hot (probably my fault for using the internal radiator cooler with a high stall converter) and input shaft decided to "unpress" itself from the input drum and created a huge internal hydraulic leak and burning the 3 - 4, rear case lugs were all chattered up upon disassembly, so i picked up another transmission at the junkyard, disassembled, cleaned/inspected, and full rebuild with everything listed in the first post. Didn't write down all my clearances but i kept everything on the tighter end.


https://globaltransmissionparts.com/...BoCL2EQAvD_BwE

Okay, let me try to go over a few basic things here to help you figure this one out.

First, with the performance kit you put in, the command for the pwm solenoid does not make any difference anymore. You can change it to whatever you want in the tune, it will do sweet nothing.

The only thing that matters now as far as lockup is the TCC enable solenoid command. Unfortunately I don't think HP tuner has a way to show what the command is for that solenoid, I have never seen a log with it, they only seem to have that goofy TCC mode parameter available. To know what the TCC enable solenoid command is happening, the easiest thing is to look at the TCC pwm percentage signal command happens, look at the PWM solenoid %. As soon as you see it drop and then ramp up, it means the TCC enable solemoir just turned ON, and now you're in full lockup.

Nest, yes, I am very familiar with that servo. Actually both of them that website you got them from includes both the second and fourth servo. With that 4th servo, you actually don't need as much pressure to apply the same force since it has a slightly greater apply surface area. So in theory you should not need more pressure then before.

The one thing that makes a difference here is how much servo travel you have. In second gear it's fairly easy to hold the drum, but because the drum turns in the opposite direction on third vs first gear, it's a harder to stop the drum. So if you have more than 0.100" ilof pin travel, it sometimes has a hard time to hold under load. Double check you travel there.

Next, the reason it holds solid even with the computer not commanding as much pressure once the lockup is applied, is because now you've just removed all the torque multiplication from the torque converter. So, it is much easier to hold the band from slipping when you're in fourth with the converter fully locked.

As for the input shaft coming out of the drum taking out your 3-4 clutch, that is an extremely common issue, and had nothing to do with using the radiator or not with your higher stall converter. With a higher stall converter, the best thing you can do is to always use the in radiator heat exchanger AND add after it a good size external air to air heat exchanger. Liquid to liquid is much much more efficient than air to air, that's why you want to have both. To help illustrate the difference, think about going outside in your boxer shorts only when it's 50? outside. Not too fully unbearable for a short period, however now think about going into water in a pool at that same 50? temperature. See how much more efficient liquid to lquid is at transfering heat? You will freezing big time!

All that to say, that you simply don't have enough clamping force to prevent thee band from slipping fourth gear with the converter unlocked. If you're lucky, you haven't driven enough yet to fry the band.

If it was me, I would double check the band clearance, if that's all good I would put a gauge on it and see what the pressure is at the lowest command by the computer versus the highest command to make sure it is in specs. If thats good I would look at the pressure on 4th gear to make sure there's no leak when in 4th.

If that all looks normal, then I would tweak tune to make sure that it commands higher pressure in fourth when the converter is not locked.

Greatly appreciate the information, i didn't post a log of it, but i did rule out the TCC, maxed out the TCC apply table and tested, and it still does it, seems strange to me, once it shifts back into 4th after dropping to 3rd, it feels solid, haven't noticed any slipping. I haven't changed any transmission parameters relating to shift pressures. Are you familiar with this servo assembly? Put the link below. Advertises 35% more apply area than corvette servo assembly. Maybe it does need more apply pressure? I am not sure if i have any old logs with transmission channels with the old transmission but i will look, i don't recall noticing this with that transmission though. Original transmission when i completed the swap was also a 4l60e, got really hot (probably my fault for using the internal radiator cooler with a high stall converter) and input shaft decided to "unpress" itself from the input drum and created a huge internal hydraulic leak and burning the 3 - 4, rear case lugs were all chattered up upon disassembly, so i picked up another transmission at the junkyard, disassembled, cleaned/inspected, and full rebuild with everything listed in the first post. Didn't write down all my clearances but i kept everything on the tighter end. https://globaltransmissionparts.com/...BoCL2EQAvD_BwE

Okay, let me try to go over a few basic things here to help you figure this one out.

First, with the performance kit you put in, the command for the pwm solenoid does not make any difference anymore. You can change it to whatever you want in the tune, it will do sweet nothing. The only thing that matters now as far as lockup is the TCC enable solenoid command. Unfortunately I don't think HP tuner has a way to show what the command is for that solenoid, I have never seen a log with it, they only seem to have that goofy TCC mode parameter available. To know what the TCC enable solenoid command is happening, the easiest thing is to look at the TCC pwm percentage signal command happens, look at the PWM solenoid %. As soon as you see it drop and then ramp up, it means the TCC enable solemoir just turned ON, and now you're in full lockup.

Next, yes, I am very familiar with that servo. Actually both of them that website you got them from includes both the second and fourth servo. With that 4th servo, you actually don't need as much pressure to apply the same force since it has a slightly greater apply surface area. So in theory you should not need more pressure then before. The one thing that makes a difference here is how much servo travel you have. In second gear it's fairly easy to hold the drum, but because the drum turns in the opposite direction on third vs first gear, it's a harder to stop the drum. So if you have more than 0.100" of pin travel, it sometimes has a hard time to hold under load. Double check you travel there.

Next, the reason it holds solid even with the computer not commanding as much pressure once the lockup is applied, is because now you've just removed all the torque multiplication from the torque converter. So, it is much easier to hold the band from slipping when you're in fourth with the converter fully locked. As for the input shaft coming out of the drum taking out your 3-4 clutch, that is an extremely common issue, and had nothing to do with using the radiator or not with your higher stall converter. With a higher stall converter, the best thing you can do is to always use the in radiator heat exchanger AND add after it a good size external air to air heat exchanger. Liquid to liquid is much much more efficient than air to air, that's why you want to have both. To help illustrate the difference, think about going outside in your boxer shorts only when it's 50? outside. Not fully unbearable for a short period, however now think about going into water in a pool at that same 50? temperature. See how much more efficient liquid to lquid is at transfering heat? You will freezing big time!

All that to say, that you simply don't have enough clamping force to prevent thee band from slipping in fourth gear with the converter unlocked. If you're lucky, you haven't driven enough yet to fry the band. If it was me, I would double check the band clearance, if that's all good I would put a gauge on it and see what the pressure is at the lowest command by the computer versus the highest command to make sure it is in specs. If thats good I would look at the pressure on 4th gear to make sure there's no leak when in 4th. If that all looks normal, then I would tweak the tune to make sure that it commands higher pressure in fourth when the converter is not locked.

[twenglish1]

Okay, let me try to go over a few basic things here to help you figure this one out.

First, with the performance kit you put in, the command for the pwm solenoid does not make any difference anymore. You can change it to whatever you want in the tune, it will do sweet nothing.

The only thing that matters now as far as lockup is the TCC enable solenoid command. Unfortunately I don't think HP tuner has a way to show what the command is for that solenoid, I have never seen a log with it, they only seem to have that goofy TCC mode parameter available. To know what the TCC enable solenoid command is happening, the easiest thing is to look at the TCC pwm percentage signal command happens, look at the PWM solenoid %. As soon as you see it drop and then ramp up, it means the TCC enable solemoir just turned ON, and now you're in full lockup.

Nest, yes, I am very familiar with that servo. Actually both of them that website you got them from includes both the second and fourth servo. With that 4th servo, you actually don't need as much pressure to apply the same force since it has a slightly greater apply surface area. So in theory you should not need more pressure then before.

The one thing that makes a difference here is how much servo travel you have. In second gear it's fairly easy to hold the drum, but because the drum turns in the opposite direction on third vs first gear, it's a harder to stop the drum. So if you have more than 0.100" ilof pin travel, it sometimes has a hard time to hold under load. Double check you travel there.

Next, the reason it holds solid even with the computer not commanding as much pressure once the lockup is applied, is because now you've just removed all the torque multiplication from the torque converter. So, it is much easier to hold the band from slipping when you're in fourth with the converter fully locked.

As for the input shaft coming out of the drum taking out your 3-4 clutch, that is an extremely common issue, and had nothing to do with using the radiator or not with your higher stall converter. With a higher stall converter, the best thing you can do is to always use the in radiator heat exchanger AND add after it a good size external air to air heat exchanger. Liquid to liquid is much much more efficient than air to air, that's why you want to have both. To help illustrate the difference, think about going outside in your boxer shorts only when it's 50? outside. Not too fully unbearable for a short period, however now think about going into water in a pool at that same 50? temperature. See how much more efficient liquid to lquid is at transfering heat? You will freezing big time!

All that to say, that you simply don't have enough clamping force to prevent thee band from slipping fourth gear with the converter unlocked. If you're lucky, you haven't driven enough yet to fry the band.

If it was me, I would double check the band clearance, if that's all good I would put a gauge on it and see what the pressure is at the lowest command by the computer versus the highest command to make sure it is in specs. If thats good I would look at the pressure on 4th gear to make sure there's no leak when in 4th.

If that all looks normal, then I would tweak tune to make sure that it commands higher pressure in fourth when the converter is not locked.

That makes sense about the TCC, servo travel was roughly a 1/16" when i assembled the transmission. I will recheck this. Currently i am only running an air cooled transmission cooler, i will connect it in series with the radiator cooler as well if its recommended, transmission temps seem to stabilize around 190 or less, I will also get some pressure readings, i'd like to add a transducer to be able to data log it, but not sure if i will. i will also look to see if i have a log with the TCC disabled, maybe it will show the 3-4 shift better since lockup usually occurs pretty quick after the 3-4 shift

[TransGo Robert]

That makes sense about the TCC, servo travel was roughly a 1/16" when i assembled the transmission. I will recheck this. Currently i am only running an air cooled transmission cooler, i will connect it in series with the radiator cooler as well if its recommended, transmission temps seem to stabilize around 190 or less, I will also get some pressure readings, i'd like to add a transducer to be able to data log it, but not sure if i will. i will also look to see if i have a log with the TCC disabled, maybe it will show the 3-4 shift better since lockup usually occurs pretty quick after the 3-4 shift

Servo travel seems to be perfect. Yes
, you can easily log pressure using a transducer with HP Tuners.

[ns158sl]

This should be a 4l60 sticky.

Again props to Robert with the insane informative descriptions!

Thanks again Rob.

[twenglish1]

Recorded another log today, this time with the TCC disabled, let me know what you think, i did some manual downshifting during the log, so thats why some of the shifts look out of place, along with a 3rd gear drive home towards the end, didn't realize i didnt put it back in OD. I still need to get a pressure gauge and or transducer to check line pressure, just wanted to see what your thoughts were with the TCC disabled. At one point it was in 4th going up a hill and at least from a feel standpoint i couldn't tell if there was any slipping, hitting the gas in 4th feels solid and responsive. Everything else in the tune is the same as the original post, only parameters changed was the TCC apply speeds.

TCC Disabled.hpl

[TransGo Robert]

Recorded another log today, this time with the TCC disabled, let me know what you think, i did some manual downshifting during the log, so thats why some of the shifts look out of place, along with a 3rd gear drive home towards the end, didn't realize i didnt put it back in OD. I still need to get a pressure gauge and or transducer to check line pressure, just wanted to see what your thoughts were with the TCC disabled. At one point it was in 4th going up a hill and at least from a feel standpoint i couldn't tell if there was any slipping, hitting the gas in 4th feels solid and responsive. Everything else in the tune is the same as the original post, only parameters changed was the TCC apply speeds.

TCC Disabled.hpl

It's doing the same thing, it shifts 3-4-3 and then you let of the gas and it grabs 4th again. Here's a screenshot where you can see the 3-4 looking at engine RPM in the green box I put. The red box next to it is when it goes back into 3rd (band lousing its grip on the reverse input drum). Then look about where i put the other green adn red box you will see why. The light blue trace is the line pressure solenoid command but it is inversely proportional to the hydraulic pressure in the unit. 100% is minimum line, 0 % is max line. As you can see at first during the 3-4 shift command it drops to 29.4% and it makes the shift. Then the computer says ok now we are done shifting I can backup hit pressure so it raises the % up to 38 or so and then the band loses its grip.

3-4.png

I don't know enough about tuning to tell how it is done but if you could change the settings so that I would not raise the % up like that after the shift the symptoms would go away. Chances are like I said before that it would be just a Band-Aid masking the real issue, but it would confirm that indeed the problem is the band having a hard time doing its job unless the pressure is commanded fairly high.

[twenglish1]

Yes i am definitely seeing what you are talking about, i appreciate the help! I am going to try and test raising the line pressure, i believe you can command the pressure control solenoid directly though VCM Scanners bi-directional functions, i have never tried it before though.

I am curious about the "Trans Calculated Gear Ratio" and how it works, any idea how this is calculated? Was just wondering cause i noticed that when it shifts into 4th calculated ratio goes from 1 in 3rd gear and drops down to around 0.4 and the rises to 0.688. Not sure if it really actually means anything though, would slipping show up as in an incorrect calculated gear ratio? Thanks again for all the help, i am really just trying to understand all i can about how this works.

[TransGo Robert]

Yes i am definitely seeing what you are talking about, i appreciate the help! I am going to try and test raising the line pressure, i believe you can command the pressure control solenoid directly though VCM Scanners bi-directional functions, i have never tried it before though.

I am curious about the "Trans Calculated Gear Ratio" and how it works, any idea how this is calculated? Was just wondering cause i noticed that when it shifts into 4th calculated ratio goes from 1 in 3rd gear and drops down to around 0.4 and the rises to 0.688. Not sure if it really actually means anything though, would slipping show up as in an incorrect calculated gear ratio? Thanks again for all the help, i am really just trying to understand all i can about how this works.

It is meaningless on those unless the lock-up is fully applied. There is no input speed sensor so the computer just makes up assuming things based on the gear command. You can completely ignore that PID when you are not in lock-up.

[twenglish1]

Here is a short log with the TCC disabled and manually commanding the force motor duty cycle to around 22%, current ended up being around 300mA. All shifts were noticeably alot firme. Still seeing the RPM fall than rise after the 3 - 4 shift, looks like now i need to get a pressure gauge on the transmission to see what the actual pressure is doing at that time

TCC Disabled Manually Commanded Force Motor.hpl

[TransGo Robert]

Here is a short log with the TCC disabled and manually commanding the force motor duty cycle to around 22%, current ended up being around 300mA. All shifts were noticeably alot firme. Still seeing the RPM fall than rise after the 3 - 4 shift, looks like now i need to get a pressure gauge on the transmission to see what the actual pressure is doing at that time

TCC Disabled Manually Commanded Force Motor.hpl

Ok it is not what I thought it was then, the pressure change was probably a consequence of what the computer was wiring happen instead of the cause. I got a think about this one. This is a really strange thing that it is doing. Do you happen to still have your OE 4th servo and cover to throw back on there for a quick test. It is not needed anyways and I have a feeling, even if I can't quite figure out why that the problem is there. If you do that, be sure to measure the servo clearance while you are there.

[twenglish1]

I will look for it and check the clearance when I get a chance, wonder if this could be a valve body issue, I found the old reverse input drum from before the rebuild and it looks roasted, not much deep scoring but very badly discolored, lots of hot streaks, wondering if this transmission had a similar issue before I rebuilt it? I just pulled it from the junkyard for a core, didn't actually run it in it's pulled condition. I removed all the valves from the valve body and cleaned everything and reassembled, made sure all valves moved freely and nothing looked worn

[twenglish1]

Picture of the old reverse input drum, i replaced it during the rebuild, also very chattered up where sun shell meshes with it

20240809_190221.jpg