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How can I tell when the torque converter locks/ unlocks?

5K views 19 replies 10 participants last post by  yellow_xj 
#1 ·
How can I tell when the torque converter locks/ unlocks? Thanks.

2001 XJ
4.0 L
AW4
 
#3 ·
It should lock in 3rd as well (at least mine does). I think in OD it is always locked.

It actually feels like 1-2-3-lockup-OD.

If you shift into "3" or "D" or whatever is one notch down from OD, you can feel lockup as a final "shift", and see it drop the revs on the tach.
 
#6 ·
It should lock in 3rd as well (at least mine does). I think in OD it is always locked.

It actually feels like 1-2-3-lockup-OD.
you must drive with the Comfort button :D (and that last step is 4th with lockup)

in Power mode it feels like 1-2-3-4-lockup

To answer the OP, it is the shift where the RPMs drop more than usual. You can tell when it happens with a couple of tests, one is to tap the brake with your left foot (as described above) and it will feel like you are tapping a clutch as the lockup disengages and re-engages. Another way is to tap the gas pedal and see if the jeep jerks--when lockup is not engaged the torque converter just spins more, but with lockup engaged the engine output is transmitted directly to the transmission.
 
#5 ·
When you are driving highway speeds with your foot on the gas, gently depress the brake pedal with your left foot..enough to activate the brake lights but not really cause drag. Be sure that you don't change pressure with your right foot on the gas. You will see your RPMs jump about 3-400 depending upon the speed.

The TC unlocks when the brakes are applied (triggered through the brake light circuit).
 
#7 ·
The TC unlocks when the brakes are applied (triggered through the brake light circuit).
Nothing better than messing with the stooopid computer. I have taken to driving in "power" mode, but in 3rd it will not lock up as early as when in "comfort". Every once in awhile if I am cruising at city speeds (50/60 km/h), I will momentarily snap the switch to "comfort" just to kick it into lockup and show it who's boss.

Now if I could just train the dumb Mopar computer to lean things out a bit so that my eyes don't water from all the stinky unburned HC in the exhaust at idle... (grumble goddam15mpgpileofjunk grumble)
 
#9 ·
On my 2001, I do not have the 'power' or 'comfort' switch. So what will the difference be when determining when the TC locks? I think I remember reading once where the later XJ's, without the power/ comfort switch, are always in the power mode, not sure though.
 
#10 ·
Yup, you have the pwr mode shift points. I think your TC locks in 3rd (feels like a shift, drops RPMs a few hundred), then you get the bigger drop in RPMs (like 800 or so) when OD kicks in.

Or, like buddy above says, maybe the little shift after 3rd is OD, and the final big shift is lockup. Maybe. You guys figure it out - like I said, that friggin AW4 won't be making my mind up for me for much longer...
 
#11 ·
i was at a stop sign and i put it in third, there is a long straight then a down hill so i was crusing at 40ish on the straight and i just happened to count the shifts: 1,2,3,...4??? I had to check again that i was in 3rd and i still was. I could never figure it out untill now..never even heard of tourque converter lockup before this lol. Still dont really understand it cept that its between 3rd and 4th?? i think

found this when i googled torque converter lockup:

The torque converter clutch is an electronic clutch that will engage the engine and drivetrain 100 percent. The TCC is made to engage usually only in the top gear when the car is cruising, not accelerating. The lock up converter will disengage when the accelerator is pressed hard enough. Over time the clutch will wear out especially if the vehicle ever towed anything and was operated in overdrive (top gear). This will wear the clutch out prematurely. If you have a tachometer you will see the RPM's drop a few hundred when it engages.
(http://ezinearticles.com/?Torque-Converter-Lockup&id=113485)

So thats why when im in 4th and i let go of the throttle the jeep jerks forward sometimes.

and this:

Many people think that this problem is coming from their engine because it causes the car to stall. The check engine light will not always show an error for the TCC. Most lockup converters are controlled by a wire or wires that plug into the transmission. It is possible on some models to simply disconnect this plug. This is not a problem and will only cause you to lose a little gas mileage. The RPM's will run slightly higher than before but will not harm anything or be an issue.
 
#17 · (Edited)
Yeah.. Does it lock up around 40-45mph though? because when i had my 96, cruising it would go into a lower rpm, and not change pitch except while speeding up.

is the lock-up anything special?


Previous poster.

SIG! thanks. i lol'd very hard
 
#18 ·
Ok im as confused as ever now. The past two days ive been searching for an answer. Here is the problem; With the cruise contol set at 60-65 driving on the highway flat ground the rpms will jump all of a suddon from 2250 to 3000 (approximation) then the cruise stops working and the rpms keep surging back and forth and i cant set the cruise again. I thought i found a solution (havent tried yet still researching) either the NSS or trans solenoid but now the Torque Converter card gets delt. BTW 01 xj 3" lift tc drop 255/75/15 tires if i missed anything its on my profile. Any suggestions?
 
#20 ·
I would agree if i was on hilly terrain but im running completely flat road no elevation changes at all so the trans should have no reason to downshift to keep up. thank you for the responce and advice.:cheers2:
 
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