4L80-E Transmission Question

[55 Nomad]

I have a 2006 C190 with the 6.0 engine and 4L80-E transmission. I don't think my torque converter is locking up. I have a Scan Gage ll installed. When I apply the brakes while keeping constant engine RPM the RPM's stay the same, doesn't increase indicating converter unlocking. I have checked at various speeds between 45 to 65 MPH. I replaced the stop light switch with a new one. All my brake lights do light up. I have 33,000 miles on it. I also changed the filter and put in fresh AC Delco GM Original Equipment 10-9243 Dexron VI Full Synthetic Automatic Transmission Fluid. I pumped out the old fluid by removing the fluid line from the radiator and running the engine while adding the fresh fluid until I saw fresh fluid. I only drove it about 3 miles before I bought it so I don't know if it was working before I did the filter. Any suggestions what to check would be help full. Thank you

[booster]

Originally Posted by 55 Nomad

I have a 2006 C190 with the 6.0 engine and 4L80-E transmission. I don't think my torque converter is locking up. I have a Scan Gage ll installed. When I apply the brakes while keeping constant engine RPM the RPM's stay the same, doesn't increase indicating converter unlocking. I have checked at various speeds between 45 to 65 MPH. I replaced the stop light switch with a new one. All my brake lights do light up. I have 33,000 miles on it. I also changed the filter and put in fresh AC Delco GM Original Equipment 10-9243 Dexron VI Full Synthetic Automatic Transmission Fluid. I pumped out the old fluid by removing the fluid line from the radiator and running the engine while adding the fresh fluid until I saw fresh fluid. I only drove it about 3 miles before I bought it so I don't know if it was working before I did the filter. Any suggestions what to check would be help full. Thank you

AFAIK, the 4L80e is not a transmission setup to unlock on brake application. It unlocks on closed throttle, probably to save fuel and increase mileage.


I think you will be able to see the lockup on the Scangauge if you watch carefully in high gear on the highway. Pick a flat section and a relatively calm day and go out and drive a steady 60mph and see what the rpm is after a couple of minutes. Let off the throttle all the way for 5-10 seconds or so and then step back on it to get to and watch the the rpm. Ours will jump up to a level under the old rpm, and then do a slower increase up a bit as the converter locks. The only way I know of to see it lockup is with a data logger like an HPtuner or such. I have one that I used to reprogram the lockup and shiftpoints on our 07 Chevy and it goes through quite a ritual to lock up with a pre lock, applying, full lock or some such.

[mkguitar]

2005 chassis


What my tranny does under operation is what Booster describes- I can hear and feel it.


I use the OBD fusion app- I just don't stare at it all time.
I set it for a tranny temp gauge and so far see no issues- my van has some B/A fans which come up coming up out of the salt river canyon on 60 in August- don;t know if they were upfitted by pleasureway or added by P/O



mike

[55 Nomad]

Thanks guys. Next time I have it out I will try what you recommend and see what happens. I would love to reprogram my transmission like you did Booster. Maybe someday.

[55 Nomad]

Will I feel it unlocking and locking on steeper grades?

[booster]

Originally Posted by 55 Nomad

Will I feel it unlocking and locking on steeper grades?

Probably, but not certainly as you don't always get just the converter unlock. You need to gently push the accelerator as you climb to try to force the unlock without getting a downshift at the same time.


If you look at the topic for reprogramming I put on this forum, it will show the lockup mph vs throttle position sensor as well as the downshift mph vs throttle position, so would be able to tell what to expect when looking for the unlock point.

[55 Nomad]

Will do that. Thanks booster

[Bjones7788]

OK "Booster the Wizard",
When I move my 2004 Chevy Roadtrek 190 with 6 L gas engine up onto vehicle ramps, I notice that putting the shifter in the lowest gear seems to result in a transmission torque converter "lock up", a desirable feature because there is less transmission slippage and throttle/power are easier to control as the vehicle goes up onto the ramps.
Is this basically the same process as high speed torque converter lock up during cruise? and if this low gear lock up occurs does that indicate that lock up in cruise is still occurring or are they unrelated?
Thanks for your wealth of previous info.

BJ
Fl Keys

[booster]

Originally Posted by Bjones7788

OK "Booster the Wizard",
When I move my 2004 Chevy Roadtrek 190 with 6 L gas engine up onto vehicle ramps, I notice that putting the shifter in the lowest gear seems to result in a transmission torque converter "lock up", a desirable feature because there is less transmission slippage and throttle/power are easier to control as the vehicle goes up onto the ramps.
Is this basically the same process as high speed torque converter lock up during cruise? and if this low gear lock up occurs does that indicate that lock up in cruise is still occurring or are they unrelated?
Thanks for your wealth of previous info.

BJ
Fl Keys

How are you determining the apparent lockup? The wheels will always turn even at idle when up in the air, the only question is how fast. How fast the wheels turn is a function of the power available to the rear wheels balanced against how much resistance the wheels have to turning. When on stands the wheel resistance is very low so they turn pretty quickly.


Torque converter speed lockup an clutch lockup are completely different. The clutch lockup directly attaches the engine to the trans solidly, but the speed lockup is a moving scale. Yep speed lockup is not always the same in any single vehicle. Speed lockup also is not 100% at any speed, even very high rpm engine speeds, which really determine the lockup point. Max lockup from rpm (engine) will be lower at slower speeds because the wind resistance is less. It will be higher at any given rpm (engine) is accelerating because the load is more when accelerating.


So bottom line is if you take an example of an 1800 rpm stall claimed converter, is probably never really at that rpm in use or between vehicles. That 1800 rated unit might lock at 1600 for a small 6 cylinder engine and at 2000 or more for a big block high output engine. This is because the definition of lockup from rpm is the rpm that with the wheels locked so no vehicle speed, the engine will not turn any faster with wide open throttle. More torque = higher stall, less torque = lower stall.


Stall speed is a hugely misunderstood and often misrepresented spec in the hotrod world and a major cause of mismatched combos of engine, gears, and torque converters, hurting performance.


My comment on no low gear lockup is based on the looking the PCM programming which does not allow it to be locked at any speed.


To put it all in line, next time you have it on stands in gear with the wheels turning, just put on the parking brake. If the wheels quit turning, the converter was not locked, if the engine dies it was locked.