4L80E torque lockup problem

[45467]

I have a 4L80E with a GM Performance controller. The combination works really well exept for the lockup converter it locks at around 70mph even though I set it up to lock after 50 mph in the controller. Anyone familiar with this controller, how do I fix this?

[Steve Chryssos]

I've never experienced that issue with any aftermarket TCU. The best place to start is by bringing up the "dashboard" screen in your software and confirming that the speedo reading matches the car's actual speed.

[MonzaRacer]

So are you using electric speedo or mechanical, if so your output speeds may ne "jive" have you tried to drop it by 10 mph andsee what happens if it comes down the TCU isnt getting proper info, while an electric speedo will be able to be recalibrated you may need allow for that, try setting it to 40 and see if it comes down if it works you just need to allow for that in setup.

[45467]

I am using a GPS as a speedo right now so the MPH indicated on the TCU dashboard corresponds with the GPS so ,I am confident that the speed is correct.I tried changing the MPH value in the TCC lockup window but it does not matter what I change it to the end result is the same. It is now set at 45MPH but it does not come on until 70mph. Does coverter stall affect the lockup feature? My stall is 2200 rpm.

[Steve Chryssos]

No, lock up has nothing whatsoever to do with stall speed. Lock up is electrically applied based on vehicle speed sensor input. If the VSS were faulty or confused by the speedo, the trans would not shift. You would be fighting a bigger battle.

So is the lock up engaging smoothly and staying locked up? I know its locking up at the wrong speed, but is it otherwise working properly?

I'm curious what happens if you go the other way with your setting: Set lock up way high, like 150mph, and then drive 70mph. Confirm that it doesn't lock up at all. That's a fairly useless test. Doesn't prove much of anything. But I'm curious. And don't leave it that way for long. Just test.

[45467]

If I keep the speed at 70 & keep climbing the lockup will stay on however, I had it lockup at lower speed but mostly when I am going up a small grade which seems odd. Is there any way to test the speed sensor.I will check if a higher setting does anything and will let you know.

[Steve Chryssos]

If the VSS were bad or confused by the speedo, your trans would most likely not upshift out of first --OR--shift at very weird times. That would bug you to the point that you wouldn't be worrying about lock up. You've made no mention of shift timing or quality, so I'm assuming that you are otherwise happy with the trans control. I have pretty much ruled out the VSS as well as other basics like system voltage and system ground. Likewise, if the lock-up solenoid were bad, I your clutch would shudder or not lock up at all. Ditto on the converter.

So if you rule out the converter, lock up solenoid, electrical supply and VSS, that leaves the TCU and it's software. At this point, you should be looking for a secondary lock up "sensitivity" parameter in the software. It should be based on TPS angle or TPS angle percentage change. Unfortunately, we deal almost exclusively in Compushift at this point, so I'm a little unfamiliar with GM's software features at this time. If you would like to call me with the software running, I'm fairly sure that we could go thru it together.

[Jake's Performance]

The GM controller is a TCI unit.

[45467]

Steve thanks for the offer. As you stated every other functions of the transmission and the TCU seem to be working as they are intended to work. The lockup is the only bug in the system. It was raining here today so I did not do anything with the car or the TCU settings . It is supposed to be a nice day tomorrow so I will try again then.

[Steve Chryssos]

The GM controller is a TCI unit.

Thanks Jake. New style or old? If it's a new style controller, then I would contact the good people at Powertrain Control Solutions for some tech. I think it would be hard to find a helpful human at GMPP.

http://www.powertraincontrolsolutions.com/

[Jake's Performance]

Steve,
The old one for sure, the new one probably, and it will probably depend on when this one was bought.

The new TCI is the PCS as you said, better unit.

Baumman has theirs setup for the GM units now also and it is cheaper than anything else available.

[45467]

Jake,Steve , my controller is GMP 12497316 . It is the older version which was produced by TCI & uses the TCom program. I will have the car out tonight to check out a few things.

[Jake's Performance]

What all do you have in the TCC screen, MPH, Lockup Rate, Delay, and WOT?

Does it only lockup in OD?

[45467]

That correct Jake. That is the info shown on that screen. Just went for a test run & changed the values from anywhere from 30 mph to 150 mph. I could get the lockup to activate at 40 mph but it would disengage after about 10 or 15 seconds. I was able to repeat this result 3 time & that was it. I also tried in performance mode to see it that would change anything but it did not. Finally I set it up for WOT & the TCC does activate but only when hitting WOT from about 60 mph . From a standing start at WOT the TCC does not engage but again I dont know if it should. I also checked the TCC solenoid for resistance & I was showing 14.5 ohms . Finally I checked the oil level & it was low by about 1 quart. I will be talking to the guy who rebuilt the trans to see what he thinks. G.L.

[Jake's Performance]

4L80E won't lock the converter in 1st gear, it isn't able hydraulically to do so.

It should be able to do so in 2nd, 3rd, and 4th though.

What all do you have commanded in the screen?

[45467]

I have the MPH set at 40 , rate 30 , delay 3.0 , lockup at wot.

[Steve Chryssos]

There's not a whole lot of lock up control in that TCOM version. MPH is obvious (although, that setting is kinda low); Rate relates to how quickly the TCC applies and releases--ramp rate. And delay prevents the lock up for re-engaging too quickly after release. 3 sec is fine if you think about how long it takes to apply the throttle, make a decision and release the throttle or vice versa. I would uncheck WOT until you resolve your issue and possibly leave it unchecked if you do not have a heavy duty lock up clutch engaging against a billet front cover. Anyway, none of this is adversely affecting the wacky apply setting.

I think I got it. :rolleyes: Let's go over your harness connections:
-The underdash TCC connector should be looped into itself--not connected to a brake pedal. And double check that you haven't plugged in the 4L60 connector.
-On the old TCI design, you need to connect both VSS connectors at the trans. Propshaft (tailshaft) and turbine (TC). To my knowledge, Compushift is the only brand that ignores the turbine input.
-Confirm that trans type is set to 4L80E in your operational parameters.

Something like one of the above is confusing your TCU.

[45467]

Thank for the suggestion Steve, I checked everything out last night and everyting check out OK. Both vss are plugged in the right location , the 4L80 E connector is into the TCU unit , the 4l80E program is selected . I reset the lockup speed at 45 , rate at 65% delay 3 seconds & the WOT applu is off. Same results ! Could there be a mechanical problem within the transmission that could cause this ?

[Steve Chryssos]

Bummer. I was really hoping to win a kewpie doll for figuring it out. I'm a computer guy. I'm not qualified to diagnose the transmission, but as far as I can tell it's not the transmission. Your issue is that it's locking up at the wrong speed. The hardware (a pwm solenoid operating a piston) is fairly dumb. It does what it's told to do. And on the input side, VSS and TPS control part throttle shift tables as well as lock up, so if the input sensors were at fault, I think you would be experiencing larger issues--no shifting.

Try unplugging the 4l80E lock up connector where it loops back into the harness to close the circuit. Inspect both halves of that connection and reconnect. Or maybe the 4l80E and 4L60E lock up connectors are labelled backwards such that you presently have a mislabeled 4l60E lock up connector plugged in. I don't know if its harmful to reverse them.

[Jake's Performance]

OK,
Steve has you on the right track.
A 4L60E and 94-up 4L80E connector has the same connector but the pinout is slightly different.
A 4L80E doesn't use a 3-2 downshift solenoid like a 60 does and there are two other wires that have to be re-pinned to convert from a 4L60E to a 4L80E but I would have to look at my notes in the shop to remember which two they are and what they control.

I doubt it is the transmission as well.

You could tie into the TCU lockup wire and have it go through a switch to ground and see if you can command lockup at will to isolate the problem.

[45467]

The transmission used is a 1991 model, could it be wired differently than a 94 & up ? I checked the wiring harness from the TCU to trans at the TCU connector & the 4L80E /4L60E connectors are on the right color wire as shown on the supplied wiring diagram The wirinharness could still be wrong . I will trace each wire to the plugs at each end to make sure they emd up on the right pins.

[Jake's Performance]

Yes,
A 1991 is wired differently than a 1994-up.
Let me get you some info to help you out, you'll likely need to drop the pan.
Someone may have updated the wiring if it was rebuilt though.

[Jake's Performance]

Sorry 1993 up is the break, 1994 they went to a different force motor and torque signal circuit.

Here's the info:
https://static1.pt-content.com/images/pt/2009/06/4L80Econnectorinfo-1.jpg

https://static1.pt-content.com/images/pt/2009/06/4L80Eextharness-1.jpg
https://static1.pt-content.com/images/pt/2009/06/4L80Eoldconnector-1.jpg

[45467]

Jake, correct me if I am wrong but the early trans had a different connector altogether. My connector is as shown on the wiring diagram for the 1993 model. Also would the rest of the transmisions performance be affected ? Everything but lockup works really well , the transmission was rebuilt & as far as I know the wiring was not changed. One last thing if the wiring was wrong I would probably get the wrong resistance reading when I check the TCC solenoid , when I checked it last Thusday it checked out at 10.7 ohms and it should be between 10 & 15 ohms.

[Jake's Performance]

Yes you are correct, the early connector used a small bolt to hold the harness to it. You must have the newer style harness and connector installed.

So you SHOULD be good. I posted this as a reference for you.

The first rule of actually repairing something is to isolate the problem.
I suspect you have a TCM or tuning issue, but if you can isolate it then you'll know for sure.

The internal harness splits the 12V Ign + to three different solenoids, the A and B shift solenoids and the TCC solenoid.
These all see constant 12V Ign power, they operate on the ground side. So you can ground the TCC solenoid wire and force it to operate independent of the TCM. This will isolate any TCC hydraulics out of the equation.
Then you can use a power probe tool or a LED to watch what the TCM is commanding and see if it matches what you feel.

I just recently did this exact diagnostic procedure on a Furd Exploder that had a weird issue that I THOUGHT was TCC related.

Another rule of thumb for trans work, the one thing you KNOW is OK and are being hard headed about, is what the problem is. :)

Maybe the diagrams will help, maybe not.

I would at least check the pinout of the TCM harness at the trans end because it differs from the 80 to the 60 and most would ship in the 60 configuration.

[MonzaRacer]

Oh god the horror I remember replacing 4L80E internal harnesses and outer ones too. I can still smell the shrinky butts glue getting hot, laying under buses!.
Yeah the harnesses has fluid leak issues too, see if you have fluid in the connector that will drive the trans NUTS!!!!
Good Luck
Lee Abel
AFTERMARKET PERFORMANCE

[turbo kid]

Have you fix the lock up problem?What was it?

[terrainman1]

I have a 1991 GMC 2500 Sierra.
The problem I have is that at 110km/hr the Transmission starts downshifting from overdrive then right back in and over and over. I had it recently into the transmission shop and after a full scan they said it was because the TPS is sending the driver demand downshift signal to the computer to shift the transmission. So I replaced both the TPS and the Computer and the problem persists.
This truck has been lifted 6 inches and has 35" tires on it now. Additionally the Speedometer was adjusted to match proper speed after the lift and tires were done.
Anyone have any suggestions what could be done to finally fix this problem. I am at my wits end and am tired of spending money with 0 results.