Torque converter clutch

[SebringLX]

Obviously talking automatic transmission here... trying to figure something out, need some auto trans experts to tell me if I am thinking correctly here.

I think I may have fried my torque converter clutch.

It was my understanding that a torque converter clutch should only lockup under cruise conditions. However I read something that indicated it will lockup under part throttle conditions as well. Can someone confirm that? If that is the case, I know I need to check my trans fluid for metal, and if I find metal in it, I'll know I most likely fried my torque converter clutch.

I still haven't figured out why the torque converter clutch would be attempting to lockup around 5000RPM in 3rd gear under WOT. It is my understanding that it should never try to lockup while under WOT. My only theory is that my PCM doesn't think it's at WOT when it really is. If the converter can lockup under part throttle, and it still thinks it's at part throttle, that is most likely the cause. I know that my PCM is supposed to see WOT as anything greater than 2V from the TPS. I am pretty sure it's close to 4V with the "pedal to the metal", however I'd have to go back and log it and look.

[turbovanman²]

Some models do have it come on in 3rd, 4th to give the engine a boost, as there is no TC slippage. Not sure what Dodge's programming is, you'd have to watch for TCC while driving.

If it is coming on under boost or WOT, then most likely you did fry it as they aren't designed for that kind of power. I am not sure if you'll find metal unless you really took it out. My A518 one went and it would simply shudder when I turned it on. Also if its really bad, you'll kill the TC and lock the stator or slow it down.

[glhs0426]

Obviously talking automatic transmission here... trying to figure something out, need some auto trans experts to tell me if I am thinking correctly here.

I think I may have fried my torque converter clutch.

It was my understanding that a torque converter clutch should only lockup under cruise conditions. However I read something that indicated it will lockup under part throttle conditions as well. Can someone confirm that? If that is the case, I know I need to check my trans fluid for metal, and if I find metal in it, I'll know I most likely fried my torque converter clutch.

I still haven't figured out why the torque converter clutch would be attempting to lockup around 5000RPM in 3rd gear under WOT. It is my understanding that it should never try to lockup while under WOT. My only theory is that my PCM doesn't think it's at WOT when it really is. If the converter can lockup under part throttle, and it still thinks it's at part throttle, that is most likely the cause. I know that my PCM is supposed to see WOT as anything greater than 2V from the TPS. I am pretty sure it's close to 4V with the "pedal to the metal", however I'd have to go back and log it and look.

The PCM should recognize anything 2.5V above idle as WOT. It's in the programming since 1984. Part throttle converter clutch is possible on your Sebring, but unless you have changed the parameters it is "light" part throttle. "Light" being something on the order of 5"HG or higher, but still accelerating.

The converter clutch on a Chrysler designed transmission operates backwards. There is fluid on both sides of the clutch piston. On the clutch side is the "release" or "off" fluid. On the other side of the piston is the apply fluid which is there doing double duty as the operating fluid for the torque converter. When lock up is desired the "off" fluid is routed through the hole in the input shaft back to the pan.

Didn't you have a very high dollar slip o four built for your car? Sounds like the converter has internal issues or there is a leak in the front pump/reaction shaft support. With the way the 41TE operates you will need to have the transmission in 2nd or higher gear to lock the converter and perform a stall test. The reason being, the solenoid that operates the L/R clutch for 1st doubles as the solenoid for the TCC.

John Roberts

[glhs0426]

Do you still have trans DTC's at full capacity? If not you might be experiencing a P1776 (Solenoid Switch Valve stuck in TCC position).

[SebringLX]

The DTCs I was able to read from it were P0700 and P0740. I've cleared the DTCs, they do not come on while under WOT, they usually come on while cruising around like your grandma would (I don't get on it at all when I have my family in the car). I have not felt any slipping, but that doesn't mean it isn't there. However, even when the DTCs are off, I still get that 1000 RPM drop right around 4700-5000RPM @ WOT. It will drop to 3700-4000RPM and backfire do to suddenly being in the wrong area of the fuel map. It seems like the converter is locking causing the RPM drop, then if I let off the gas and get back on it, it unlocks and continues as normal.

I can't see any of the trans parameters. Default value for WOT TPS voltage is 2.33V. I had lowered it to 2V, no telling if that worked as intended though. I hit quite a bit of boost with less than 25% throttle, I'd have to log to voltage to see where it's at, but I barely have to touch the gas at all to get into boost. I know in the 25-50% throttle range I can hit 20psi! I was thinking maybe the torque converter locked up while I had some high PTB, and maybe damaged it there.

How would I go about performing a stall test? I have converted it to auto stick, so I can manually shift to 2nd or 3rd. I have launched the car in 2nd before, got better 60' doing that, but was told I should avoid doing that, so haven't done it since, only did that maybe 4 or 5 times.

[Vigo]

Wow. Im surprised you got this far into 604s without knowing about this. Most of the newer cars with the smaller motors will go into lockup in 3rd, some at part throttle, some at WOT.

For example, my 96 avenger would go into lockup shortly after shifting into 3rd at WOT. That's normal operation of the car.

Although, for you to be dropping 1000 rpm from the converter locking up at 5000 engine rpm means you have a LOOOT of converter slippage at an rpm where it should have relatively little. I wouldnt be surprised then to find out that when you are upshifting at 6500 your input shaft is still turning in the 5s. Your converter should be tighter at that rpm unless you are using it as a race car.

Anywho, the simplest thing to do is the brake light switch mod.

The brake switch has at least two circuits. One lights up the tail lights, and the other tells the tcm not to lock the converter while you are on the brakes. You simply wire a switch (probably a pressure switch to detect boost in your case) which breaks that circuit while you are accelerating in boost to make the tranny think you are on the brakes, so it doesnt lock the converter. I dont know if the circuit is normally open or normally closed off the top of my head, but its simple enough to figure out with a test light or meter. As long as you are NOT in boost the clutch should handle whatever you can throw at it, and its probly doing you a big favor with that high rpm converter slop.


Also, if you really have burnt out the converter clutch, your fluid would be VERY dark (brown to black) and it would smell even worse than normal burnt ATF does. If you dont have these symptoms, i would assume there is still some life in it, and try to prolong that with the pressure switch mod.

[SebringLX]

Interesting Vigo... The newer ones are renamed to 41TE though.

I should be able to check the fluid color through the dipstick on the trans right? Last time I checked it, it was still that translucent purple color that Mopar ATF+4 is. Only about 7K miles on this fluid and the trans since it was beefed up. I was thinking I would have to drop the pan to get some fluid and look for metal flakes in it, but if I can check it by wiping some on a paper towel from the dipstick, that's a lot easier. I have about half a case of ATF+4 left from when I first filled it after getting the car back.

The converter I had put in is supposed to have a 3400RPM stall IIRC. At 5000RPM and 22psi, I'm probably making well over 300HP to the wheels.

I wonder if I could wire the "brake light switch mod" in with the autostick sensor somehow. I only go WOT like that with the car in autostick mode. So if I could wire it up to activate the switch when I put the gear selector all the way back for autostick, that would work well. The rest of the time (driving to work, gocery store, etc) I always have it in drive.

So doing that mod won't make my brake lights turn on will it? Not a big deal at the track, but I'd hate for my brake lights to be on when I'm not braking driving around if the switch was active.

[Vigo]

I think i came off badly, sorry. Im surprised you didnt notice it when the car was stock, not that you did or didnt 'know' something. But now that your converter is looser the difference is too big to overlook, makes sense. I had a 3300 stall in my intrepid and i also felt that that converter was too loose at high rpm and i was losing a bunch of high rpm power through it.

The actual brake lights are on a seperate circuit that goes through the same switch, at least on all the older cars. I havent tried it on a newer car like yours.

I think the autostick thing is a good idea, but i dont know what the transmission range switch output looks like and how you could run anything off of it. I guess you'd have to look at a wiring diagram that shows the inputs and outputs of the TRS and see if it is just something simple like the old park/neutral switches. If so you could just run that to the coil side of a normally open or normally closed relay and put the other side between the brake switch and the tcm somewhere.

[glhs0426]

Good info Vigo! I did not know about WOT lock up. A Hobbs switch would work great on this ciruit, or a micro swich installed to interrupt the ground when placed in AutoStick would also work great.

The AutoStick uses hall effect signals to the TCM to signal an upshift or downshift request, so, that part of the circuit is out. There is power to the AutoStick from fuse 11 in the Junction Block. The AutoStick also has a ground.

The part of the brake switch Vigo referred to is just used for the NGC controller and the Shift Interlock. This part is normally grounded and is not grounded when the brake is pressed.

I will send you an email with the wiring diagram attached.

John Roberts

[SebringLX]

OK so when the ground to the brake switch is interrupted, the TCC is not allowed to lock.

Now what about the AutoStick switch, is it in AutoStick mode when grounded, or is it in AustoStick mode when the ground is interrupted?

Er wait, I see what you're saying here... Mount a microswitch on the shift assembly, so that when the shifter is all the way back it will depress the switch and interrupt the ground to the brake switch... like a momentary switch... when the button is held down (shifter is up against it), the circuit is interrupted, then the shifter is moved away, the button releases, and circuit is grounded again?

[SebringLX]

I had another idea on the way to work... What about using a WOT switch from a nitrous kit for this? I have a Zex wet kit in my garage, I believe there's a WOT switch in with it somewhere. I wasn't planning on installing it any time soon, but maybe I could use the WOT switch from it for the brake switch mod?

Also if I'm reading this correctly, the wire I'm looking for is white/pink (it says WT/PK) coming out of pin 23 on the connector to the PCM? What connector though? There are 4 connectors on the PCM...

Actually it looks like it may be easier to find the "Brake Transmission Shift Interlock Solenoid", as I'm sure there are less wires going to that than there are going to the PCM.

[Reaper1]

If you use a WOT switch, try to use an electronic one! I've had nothing but problems with my mechanical one in my car for my 2-stage boost control. It NEVER stays adjusted correctly, so when I REALLY want high boost when I hit WOT...sometimes it works, sometimes it doesn't! So, for now I just bypass it, which sucks.

[RoadWarrior222]

Turning up the line pressure fixes everything

Well seriously, it might help, my TC troubles have only been while experiencing pressure drop for some reason or other. Also I believe I've read that upping the pressure will tighten the converter higher up... anyway, combo of the two might mean less RPM drop, which might be livable.

[Reaper1]

The issue with that is that the 41TE monitors the line pressure. The stupid TCM will send it in to limp mode if it sees too much pressure in certain circuits inside the tranny.

[SebringLX]

No TCM on my car, just a PCM... ECU/TCM functions are combined into a single unit on the NGC vehicles.

Anyway, same thing would happen... I don't have the ability to adjust the line pressure parameters in my PCM. I can on JTEC vehicles, but they never added that for NGC vehicles.

[Reaper1]

OK..I'm dumb...what's a JTEC? LOL

[SebringLX]

OK..I'm dumb...what's a JTEC? LOL

JTEC = ECU for 96-2002 gas powered Dodge and Jeep trucks/SUVs.

NGC is the PCM for all 2003+ Dodge/Chrysler/Jeep vehicles.
NGC1 for 2003 to mid 2004
NGC3 for mid 2004 on up.

[Reaper1]

Thanks for the run down! I knew what NGC was, but I didn't know there were 3 different classifications! Now I know...and knowing is half the battle!

[Vigo]

IF you do use a physical switch, may a recommend... another brake switch? Hehe.

The wot style switch has a very small range of motion and has to be adjusted just right to work.

Something like a brake switch actually actuates the circuit early in its travel and then can keep going, meaning you could set it up to where there was a constant spring pre-load pushing on the shifter, meaning if it moves a little or the shifter itself doesnt land in the exact same spot every time, it will still work.

just a thought.


I would also like to point out that i have done this with just a regular switch on the dash, but i constantly forget to put it back into lockup mode since my stock converter in the dynasty is so little rpm difference between locked and unlocked. On a higher stall converter it would be obvious when you'd forgotten to switch back, so that could be the k.i.s.s. solution.

[glhs0426]

OK so when the ground to the brake switch is interrupted, the TCC is not allowed to lock.

Now what about the AutoStick switch, is it in AutoStick mode when grounded, or is it in AustoStick mode when the ground is interrupted?

Er wait, I see what you're saying here... Mount a microswitch on the shift assembly, so that when the shifter is all the way back it will depress the switch and interrupt the ground to the brake switch... like a momentary switch... when the button is held down (shifter is up against it), the circuit is interrupted, then the shifter is moved away, the button releases, and circuit is grounded again?

Exactly!

I had another idea on the way to work... What about using a WOT switch from a nitrous kit for this? I have a Zex wet kit in my garage, I believe there's a WOT switch in with it somewhere. I wasn't planning on installing it any time soon, but maybe I could use the WOT switch from it for the brake switch mod?

Also if I'm reading this correctly, the wire I'm looking for is white/pink (it says WT/PK) coming out of pin 23 on the connector to the PCM? What connector though? There are 4 connectors on the PCM...

Actually it looks like it may be easier to find the "Brake Transmission Shift Interlock Solenoid", as I'm sure there are less wires going to that than there are going to the PCM.

You would want to install the switch on the ground side of the brake switch. The wiring for the BTSI and PCM is spliced before the brake switch so opening the ground on one of the WT/PK wires would be useless.

The issue with that is that the 41TE monitors the line pressure. The stupid TCM will send it in to limp mode if it sees too much pressure in certain circuits inside the tranny.

Yes and no. The very late ('06? some models, '07 more, '08 all 41 based trans) actually monitor line pressure and adjust it just like the JTEC trucks/Jeeps. The earlier 41TE will just go to limp mode if a pressure switch is tripped in a monitored circuit at the wrong time. I think the switches have a 20psi threshold.

After talking with my old boss today we came to the conclusion raising the line pressure may indeed help, but if it was not doing this before and now it is, something is wrong (internal leak).

John Roberts