: Torque converter.



miwise
12-24-10, 02:14 PM
I dont think my tbc is engaging. Doesn't go into lockdown. What could cause this?

Submariner409
12-24-10, 02:48 PM
TCC - Torque Converter Clutch - is set by a solenoid and hydraulic pressure. If the solenoid itself or the electrical circuit which control it is/are bad, a code will set. Use your car's built in code reader/scanner to check - you're looking for P0740, 41, 42, 43 codes.

To mechanically check the system, get on a long level stretch of highway at 60 mph. While maintaining steady speed with your gas pedal (not cruise control) touch the brake pedal with your left foot. Does engine rpm increase by about 300 ? if so, TCC is operating. As soon as you release the slight brake pedal touch the rpm should again drop by about 300 rpm.

If TCC is operating - also..........your engine will show 2,000 rpm at a steady 60 mph.

Ranger
12-24-10, 03:25 PM
Actually any speed above 41 MPH will do for the test Sub mentioned. That's the speed at which the TCC engages.

miwise
12-24-10, 06:26 PM
Ok. Thx. I tried that test earlier but failed. Just did it again and pass. Hmm. Maybe it's just me. Lol. No codes for it. I do have p0135 147 146 along w misfire code tho.

Dadillac
12-24-10, 06:32 PM
I just recently had my trans replaced and couldn't resist doing the TCC test. I haven't been able to do it for about 5 years. Between 41 and 55 mph when you do the test you will see a 300 or so rpm jump. While going 70 t0 80 mph you barely see a 100 rpm jump. I thought this strange. But I guess that the faster you go the less effective the TCC is. So you will save more fuel driving reasonably than driving with the flow of traffic. Well at least in NJ on the interstates 75 to 85 is the flow of traffic

Don

mhamilton
12-25-10, 04:25 PM
In addition to the solenoid going open, the seals to the torque convert themselves can leak hydraulic pressure and cause a loss of lockup. There are a few different codes associated with the TCC failure, one that says "TCC stuck off" and the other is for the solenoid failure. It's very possible that it fails to lock only when hot (I have this issue), but will lock up when you first start driving. With that, the code may not ever set. It has to be a few consecutive failures before a CEL will pop up.


While going 70 t0 80 mph you barely see a 100 rpm jump. I thought this strange. But I guess that the faster you go the less effective the TCC is.

You should still see the same jump. What RPM are you running at 75 mph? If more than 2000 rpm in the SLS, then your TCC is slipping.

Another way to check the TCC is after reaching cruise speed over 45 mph, with a constant road speed the RPM will remain constant unless you force a downshift (or unlock). So up and down hills the RPM at 55 in my car is 1500 when locked. If unlocked or slipping, you'll see drops in RPM when you let off the gas, and it'll rev up to 2000 when going up hills.

miwise
12-25-10, 08:30 PM
Then my torque converter is indeed slipping. :-(

Ranger
12-25-10, 09:19 PM
Another way to check the TCC is after reaching cruise speed over 45 mph, with a constant road speed the RPM will remain constant unless you force a downshift (or unlock). So up and down hills the RPM at 55 in my car is 1500 when locked. If unlocked or slipping, you'll see drops in RPM when you let off the gas, and it'll rev up to 2000 when going up hills.
Huh? :hmm: Seems to me that the RPM should always decrease down hill and increase up hill, locked or unlocked. It takes more RPM to maintain a constant speed going up hill and less down hill. What am I missing?

miwise
12-25-10, 10:26 PM
If I'm not mistaken then the torque lockdown reduces the transmission slippage to nothing. Maybe my reasoning is wrong but rpms should remain constant. I do about 2000 rpm most of the time at 60. When the car is cold it seems to be about 2300 rpms at 60. The slightest acceleration and either the torque converter is disengaging or somethings slipping. Idk. Just curious.

miwise
12-25-10, 10:28 PM
Beginning to wish I'd never messed with this car. Bc now it seems I need a new heater core too. New shocks on top of that. Who knows what else. Now maybe transmission work. Ugh.

miwise
12-25-10, 10:28 PM
The heater core is no small job. The entire dash assembly must be removed to access it. :-(

Submariner409
12-26-10, 09:39 AM
If I'm not mistaken then the torque lockdown reduces the transmission slippage to nothing. Maybe my reasoning is wrong but rpms should remain constant. I do about 2000 rpm most of the time at 60. When the car is cold it seems to be about 2300 rpms at 60. The slightest acceleration and either the torque converter is disengaging or somethings slipping. Idk. Just curious.

............but because TCC only operates at fairly low-load road speeds, ANY load change at hills other than a long Interstate rise drops out TCC and the 4th gear takes over. Yes, engine rpm will increase going up hills, and will decrease when you let off the gas going down hills. The TCC brake pedal "test" only works on a level road at steady speed, no cruise control.

Cold, and under any condition other than light load acceleration, TCC does not operate/will drop out.

I have often pondered the worth of installing a TCC pushbutton, similar to the 2000+ Traction Control button: You could then put the stick in D (for suburban driving) and TCC would not then be constantly working at various speeds at and above 41 mph or do. Would probably set codes though - maybe not, as the circuit would not be powered beyond the switch; the circuit is tripped by the PCM in response to speed and load. By habit, as soon as I pull off Rt.50 near home, during back country casual driving, and in a city I shift to 3 and leave it there. No TCC and the transmission gets a break from trying to constantly shift between 3 and 4.

mhamilton
12-26-10, 10:10 AM
Huh? :hmm: Seems to me that the RPM should always decrease down hill and increase up hill, locked or unlocked. It takes more RPM to maintain a constant speed going up hill and less down hill. What am I missing?

When the TCC is locked it's like having a manual transmission (minus some negligible slip in the viscous TCC). The RPM won't change if you're keeping a constant road speed.

What Sub said is true if the TCC is unlocking up hills that are steep enough. It is designed to do that under increasing load. But I often drive over hills that do not cause an unlock, and RPM is constant. Same with downhill, if it stays locked it keeps constant RPM. As soon as I touch the brakes going downhill the RPM drops to 1000 (say at 55).

My TCC usually doesn't unlock unless it's a very steep hill, or low speed. If I'm going 55mph+ it typically has enough momentum and I only have to give it a little gas. If I were driving the same hill at 45 I'm certain it would unlock or even downshift.

miwise
12-26-10, 01:41 PM
Very good info. More confident in my tranny now

miwise
01-06-11, 09:39 AM
Seems I may be having problems. Sometimes my torque converter locks. Sometimes not. Yesterday was warm today cold. Idk if that's why but I'm sure it's not going into lockdown today. Otherwise shifts greAt

mhamilton
01-06-11, 10:26 AM
Seems I may be having problems. Sometimes my torque converter locks. Sometimes not. Yesterday was warm today cold. Idk if that's why but I'm sure it's not going into lockdown today. Otherwise shifts greAt

That's what mine does... when the fluid is cold it always locks. When I get over 65 mph it locks (high pressure). But if I've just driven 30 miles on the interstate in stop and go traffic and then drive around town (over 40 mph) it won't lock like it should. I know my problem is with the seals... obviously they are leaking slightly, so when the fluid is thick it works, but when thinned from heat it leaks too much to apply the TCC.

miwise
01-06-11, 10:52 AM
Hmmm. Guess I'll be working on that next. Lol

miwise
01-06-11, 11:27 AM
And now it works.

Ranger
01-06-11, 03:19 PM
I have yet to nail down EXACTLY when I get the SES light and P0741 code. I THINK it seems to be while in cruise and MAYBE on a slight incline, but still not sure.

miwise
01-06-11, 04:01 PM
I never get a light.

Ranger
01-06-11, 09:11 PM
Really? The TCC stuck on or off should set a DTC and trip the SES light.

tateos
01-06-11, 09:24 PM
I have yet to nail down EXACTLY when I get the SES light and P0741 code. I THINK it seems to be while in cruise and MAYBE on a slight incline, but still not sure.

Oh - I didn't know you were having this problem Ranger. And on a 2003? I thought it was mostly on the older cars. Well, now that I think of it, a 2003 IS an older car nowadays... I guess

Ranger
01-06-11, 11:02 PM
Yeah, I've been getting the code for about a year now. It's getting more and more frequent it seems. :(

mhamilton
01-07-11, 10:10 AM
I've got mine intermittently, so I've only seen the CEL once or twice. If I clear it, P0741 comes back as a current code, but I think it takes 3 or more consecutive failures to illuminate the CEL. With mine, by the next time I take the car out the TCC is locking again. It's probably constantly cycling between Current and History. I'm sure it confuses the poor PCM...

If your TCC never locks (or rarely locks) it will certainly set the CEL.

Ranger
01-07-11, 12:03 PM
It takes 3 or more successful checks to CLEAR the code and turn off the CEL. I believe the code will set and the light will come on at the first failure.

mhamilton
01-07-11, 04:52 PM
Yes, that is true about the CEL going off by itself. The 2 times the CEL came on I cleared the code manually. But the 741 will come back as current code without my CEL light coming on.

I'm not sure what the FSM says, but it seems to take some miles driving with the TCC unlocked before I get a CEL. It could be the PCM programming was changed in later years to eliminate that delay.

miwise
01-07-11, 08:04 PM
Just noticed it primarily happens the first hundred mi or so after clearing codes. I've cleared codes several times tho bc I've been working on lots of other problems as well. Maybe I haven't driven enuf miles yet to set a code. I do know it seems to work sometimes and not others. I think I may start keeping a notebook in my car to log this info and keep track recording temps and other variables. Ugh

Submariner409
01-09-11, 10:15 PM
Best bet ??? NEVER "clear codes". Keep a notebook once a month or so. Most codes come and go like clouds - here today, gone tomorrow. A serious fault will set a light - otherwise you'll go paranoid if you habitually pull and clear codes. I haven't cleared a single code since sometime in '06, according to my log, and at 4 PM today there were none set, and that's after a quickie run to 115 mph.