Lockup Slip at 55

[400Horses]

I don't have a scan to share at this time because I think my question can be answered without one. I have a new built 4l60e transmission in a 99 silverado. I have done the bluecat tune adjustments, and the trans functions the way it is suppose too except.... At 55mph when the converter is suppose to lockup it will slip and cause the pressures to go up on the 1-2 shift. Pressures drop back to normal after shutting the truck off. This issue only happens at the 55mph lockup. Above and below 55 the convertor does what its suppose too. There is no shutter or surging associated when driving the truck. I do have to finish tuning the MAF past 4k rpm, but have to get the new injectors in first due to a lean issue past 4k. Thanks for any help. I can get a new scan this afternoon if it is needed to help with my issue. Thanks in Advance

[TheMechanic]

Got to at least give us the tune. Could be a real simple setting or it could be a bad converter

[400Horses]

Sorry for taking so long on posting the tune. Alot going on in the driveway.

[TransGo Robert]

Sorry for taking so long on posting the tune. Alot going on in the driveway.

If you could also take a log with all the transmsision parameters showing when it is doing it at 55 and when it is fine above 55 it would help a lot. It sounds to me like a classic case of worn TCC Regulator valve bore resulting in P1870 and high line until you cycle the key, but without looking at a log I can't say 100%.

[400Horses]

I can try to get another scan but it doesn't do it all the time. The transmission though is a fresh rebuilt unit that I had upgraded to level 2 by performabuilt. I will post something as soon as I can. I also have an 03 Tahoe that just lost a rod bearing and an 08 tahoe that I just purchased that is showing some issues that I am also working on. I can share my last scan for you to look over and see what might stand out to you, or if there are any PID's I need to add.

[TransGo Robert]

I can try to get another scan but it doesn't do it all the time. The transmission though is a fresh rebuilt unit that I had upgraded to level 2 by performabuilt. I will post something as soon as I can. I also have an 03 Tahoe that just lost a rod bearing and an 08 tahoe that I just purchased that is showing some issues that I am also working on. I can share my last scan for you to look over and see what might stand out to you, or if there are any PID's I need to add.

Ok thanks for the log, that's it is is a TCC slip issue. In that recording it was not bad enough to set a code and make it command high line because the unit was still only at 140F and you were driving it at very light throttle, but the problem was there clear as day in the data. The command is trying all it can to bring the slip down to zero, it is maxed out at 96% but you always have a 40-50 rpm of slip with only 6% throttle and as soon as you go up to 8% it the slip goes to 80-90 rpm. The shop that rebuilt it missed something, I would have them diagnose the issue, this is not a command issue. If you do take another log be sure to also log the force motor solenoid (pressure control solenoid) command , it will not cause this issue at light throttle but it would be good to look and make sure all is commanded properly so that the rest of the unit does not end up suffering.
Slip.png

[400Horses]

It is suppose to storm in my area this weekend so I may have to wait a little longer to get another scan. I wanted to ask though if the converter clutch could possibly cause the same issue?

[TransGo Robert]

It is suppose to storm in my area this weekend so I may have to wait a little longer to get another scan. I wanted to ask though if the converter clutch could possibly cause the same issue?

95% of the time the converter is the victim not the cause of the issue.

[TheMechanic]

95% of the time the converter is the victim not the cause of the issue.

Really? With a 4L60e? Can you educate me more on this O trans Guru. Said with the most respect. Not a transmission guy. I thought most TCC apply issues were TC clutches.

[TransGo Robert]

Really? With a 4L60e? Can you educate me more on this O trans Guru. Said with the most respect. Not a transmission guy. I thought most TCC apply issues were TC clutches.

Same thing has any other clutch, they usually fail because there is either not enough clamping force to prevent if from slipping or they don't fully release causing them to drag and burn. The 95 and 4L60E is notorious for wearing out the valve body at the TCC regulator valve bore resulting in not enough pressure sent to apply the converter clutch causing it to slip and burn. There are other areas in the transmsision that can also cause it, but the TCC regulator valve bore wear is the cause in probably 95% of them.

[TheMechanic]

Same thing has any other clutch, they usually fail because there is either not enough clamping force to prevent if from slipping or they don't fully release causing them to drag and burn. The 95 and 4L60E is notorious for wearing out the valve body at the TCC regulator valve bore resulting in not enough pressure sent to apply the converter clutch causing it to slip and burn. There are other areas in the transmsision that can also cause it, but the TCC regulator valve bore wear is the cause in probably 95% of them.

So can anything be done for longevity sake? Just an increase in pressure or less in the PWM of the pressure solenoid? Or is it just one of those things?

[TransGo Robert]

So can anything be done for longevity sake? Just an increase in pressure or less in the PWM of the pressure solenoid? Or is it just one of those things?

The pressure is not an issue, raising it would not help anything. The problem is the same with every PWM system in modern transmissions, the constant pulsing cause the valve to oscillate constantly wearing out valve bores, so eventually you have to fix the bore. In this specific case the transmsision can be modified to completely eliminate that valve and solenoid and make ON/OFF no matter what the computer commands, but I am not a fan of how it feels.

[TheMechanic]

The pressure is not an issue, raising it would not help anything. The problem is the same with every PWM system in modern transmissions, the constant pulsing cause the valve to oscillate constantly wearing out valve bores, so eventually you have to fix the bore. In this specific case the transmsision can be modified to completely eliminate that valve and solenoid and make ON/OFF no matter what the computer commands, but I am not a fan of how it feels.

Seems to me I remember the trans guys when I was at the dealer that there was some kind of sleeve or something that they did to some valve body. Maybe it was an updated VB

[TransGo Robert]

Seems to me I remember the trans guys when I was at the dealer that there was some kind of sleeve or something that they did to some valve body. Maybe it was an updated VB

Yup when it worn out one of the many options is to oversize the bore, put a sleeve and a redesigned valve to bring it back to working as intended.