detecting torque converter lock up?

[pasadena_commut]

Is there some way to tell if the automatic transmission's torque converter is locked up?

Some people in this forum have discussed the pros and cons of when this lock up occurs, but so far I've not found a post describing how they knew the internal state of the torque converter while driving.

 

[joey]

Start moving from a stop and watch your tach. You'll see the RPMs drop at every shift. You'll also see them drop once without the transmission shifting. That it the Torque converter locking up. It should happen after you hit 4th gear.

 

[pasadena_commut]

Start moving from a stop and watch your tach. You'll see the RPMs drop at every shift. You'll also see them drop once without the transmission shifting. That it the Torque converter locking up. It should happen after you hit 4th gear.

Thanks.

Is TCC the term used for torque converter lock up in the online manual, for instance in 05-17-15? [EDIT: or is it cruise control, in which case, never mind...] If so the diagram there for the FS engine shows this kicking in at around 35 mph during light acceleration, and staying on down to about 34 mph. If that is torque converter lock up then it would seem that driving at 33 mph won't be much more efficient than 32 mph, and 37 mph won't be much different than 36 mph, but 36 mph should be a lot more efficient than 34 mph. That suggests that the best mpg in city driving would be achieved by getting up to 36 mph fairly quickly so that the lock up kicks in and the converter losses decrease, as opposed to accelerating like a granny and taking forever to get up to that speed.

The online manual is for a 2002. Are the shift points for the 2003 transmission (the one without the OD button and with sport shifting) close to those shown in 05-17-15?

 

[pasadena_commut]

You'll also see them drop once without the transmission shifting. That it the Torque converter locking up. It should happen after you hit 4th gear.

At roughly what speed should this occur?

I've tried this a couple of times and have yet to see an RPM drop any time after it enters 4th. Or at least I didn't notice it between 35mph (in 4th) and 75mph.

Does the protege have a torque converter lock up solenoid, and if so, can it be tested (for short or open) without pulling the transmission?

 

[pasadena_commut]

Anybody?

Google turned up a nice article that defines TCC (something the shop manual doesn't do):

http://ezinearticles.com/?Torque-Converter-Lockup&id=113485

The TCC is the torque converter clutch and it is the part that is responsible for torque converter lockup. The shop manual shows the TCC range as the shaded region in the diagram on page 05-17-05. In my driving tests I've not been able to see the supposed drop of several hundred rpm when the TCC engages when cruising in 4th above 37mph. Possibly it is engaging very quickly and it is merged in with the drop in RPM I see when the gas pedal is eased up slightly to stop accelerating and maintain a constant speed? If that's the case it is going to be very hard to distinguish between the TCC working quickly and not working at all.

Or to put it another way, if the TCC was completely nonfunctional, would there be any symptom other than decreased gas mileage?

 

[i12drivemyMP5]

The easiest way to notice this is be in 4th in manual mode at a cruising speed/rpm then punch it, it should seem like it subtly downshifts into a passing gear then the same change back when you ease up on the gas & cruising again. I suppose you might lose a small amount of mpg on long freeway drives. Seems harder to notice in auto mode because if you punch it it will drop into passing gears, it just seems like an extra gear change once cruising.

 

[Onatrum]

So basically, the converter locking up is when overdrive engages? If this is true, then I would agree that mine locks up at around 35 or 36 mph. If you have any exhaust that makes a noticable sound in the car, you should be able to hear the subtle change in tone when the overdrive engages. My 02 P5 has the overdrive on/off button, and I usually play with this if I know I'm going to pass somebody on a country road and need a quicker response.

 

[pasadena_commut]

The easiest way to notice this is be in 4th in manual mode at a cruising speed/rpm then punch it, it should seem like it subtly downshifts into a passing gear then the same change back when you ease up on the gas & cruising again.

Too subtle for me - step on the gas the revs go up, step off the gas the revs go down. Couldn't see the TCC in that. However, I finally did spot the TCC working by putting the transmission into 4th and accelerating very slowly from 34 at constant RPM. At about 38 mph the RPMs dropped by about 200. The tiniest change in gas pedal pressure was enough to kick the RPMs up or down by that amount.

My car makes a sound like a turbine winding down at around 36 mph (plus/minus) when it is slowing down from above 40 (ease off the gas, no brakes). Sometimes. It's pretty high pitched and not very loud, I can only hear it with the radio off, no traffic around, and the window down. Is this maybe related to the TCC releasing?

 

[i12drivemyMP5]

I don't have any sounds like that..........

 

[mogi]

sure you aren't hearing the tranny whine at the specific RPMs?

 

[pasadena_commut]

sure you aren't hearing the tranny whine at the specific RPMs?

The only time it's audible is under the circumstances described above: never when driving faster or slower and never when maintaining speed or accelerating up through that range. It may well be a resonance in the automatic that kicks in then and "whine" is as good a description of the noise as any. However since it only does this (when it does do this) at more or less the point where the TCC should be releasing I thought it might be related.