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Is there a precise way to know if/when my torque converter is locked up/unlocking on a Nissan Maxima 2002?

Most answers I've found over the internet is "by feeling". For instance, "when this situation X occurs, it will unlock", or "when you reach about speed Y, you'll feel a little boost -- that's when it's locking". That's not quite precise and I've not been able to "feel" it.

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  • Are you asking this to see if yours is working correctly, or just generally want to know "when" the lockup/disengage occurs? – Pᴀᴜʟsᴛᴇʀ2 Mar 20 '14 at 21:09
  • I'm curious to observe at which moment it is locked up and at which moment it is disengaged. I wouldn't have a clue as to know if mine is working correctly... answers to this would probably help me figure it out. – user4534 Mar 20 '14 at 21:26
  • I think the problem you are going to have is that "seat of the pants" you are not going to be able to tell. It would be so subtle you wouldn't notice. The PCM will cause it to go in/out of lockup. The only way you'd be able to tell is by having a computer attached to your the car and see when the PCM gives the signal to the tranny for the lockup. One thing you have slightly wrong in your question is the lockup will disengage when the car "needs a little boost" ... it locks up to give better gas mileage. – Pᴀᴜʟsᴛᴇʀ2 Mar 20 '14 at 21:56
  • Ah, yes! But I was thinking about when it locks up when the car is going from idle to cruise speed; from what I could fetch, the TC will never be able to have a 1:1 ratio unless it is locked up, so when the lockup occurs, there is a small boost felt when the transmission gets up to speed with the engine. Thanks for your input! Now I want to plug my car to my PC :P – user4534 Mar 21 '14 at 0:13
  • When the TC locks up, it is very close to 1:1 already. When I say it's subtle, it's very subtle. I'm not sure of the programming, but would believe this is only going to happen in the final gear (if a 4 speed tranny, it will happen in 4th gear, etc). Also, your transmission will not catch up to the engine, your engine will slow down to your transmission, and then only by a couple hundred RPM at most. This is probably going to be your only indication that your TC has locked up. – Pᴀᴜʟsᴛᴇʀ2 Mar 21 '14 at 10:18
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(Moved some comments down here as an answer.)

I think the problem you are going to have is that "seat of the pants" you are not going to be able to tell. It would be so subtle you wouldn't notice. The PCM will cause it to go in/out of lockup. The only way you'd be able to tell is by having a computer attached to your the car and see when the PCM gives the signal to the tranny for the lockup. One thing you have slightly wrong in your question is the lockup will disengage when the car "needs a little boost" ... it locks up to give better gas mileage.

When the TC locks up, it is very close to 1:1 already. When I say it's subtle, it's very subtle. I'm not sure of the programming, but would believe this is only going to happen in the final gear (if a 4 speed tranny, it will happen in 4th gear, etc). Also, your transmission will not catch up to the engine, your engine will slow down to your transmission, and then only by a couple hundred RPM at most. This is probably going to be your only indication that your TC has locked up.

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