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Discussion Starter #1
I am looking for info on when and how the torque converter locks up. I have found speeds of 45 and also 62 mph on the Frontier. Curiously, the manual says you can shift into 4high under 62mph, so might that be TC related? 62 seems awfully high for lockup.

Is there any aftermarket electronic devices that control the transmission? On other trucks you can set a tow mode, or make the TC lockup sooner/ at lower speeds. (for auto diesels they lock the TC for their exhaust brakes to be used for example, for towing they want their trucks to lock at lower speeds).

I drive a lot of backroads where the speed is right at/over/below the 45mph speed, so knowing when the TC might be locked will be helpful.
If it IS at 45mph then I would want to keep speed above 45, but if at 62 then it doesnt matter, but I would want to have it lock at a lower speed.

I just can't find any info out there..
 

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You need to download a copy of the service manual at nico club. there's a hundred or more pages on how your TC lockup works and all the secondary systems to control it. The 2.5 only locks in 5th, 4.0 locks in 3-4-5. Then theres soft and hard lockupps . Theres about 15 different PN's for TCM's and on and on.
 

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Discussion Starter #3
Well, that's better than the forum guy that always says to every post ever, "go look it up on the internet".
The nico club site has a lot of info, I saved the link, but the few hundred of pages I scanned over did not yield the info I was interested in yet, gleefully, there are thousands more pages to look through one day.

In the meantime if anyone knows a quick answer then feel free to post it here, or a specific link,
thanks
 

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yea, alot of info,but did you figure out how to get the svc manual downloaded to your device so you dont need to be online to use it.
 

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Discussion Starter #5
I have not put it on the phone, but that is a good idea...

Driving around I am playing with the TC, and see it seems to be locked at 33. Lower is hard to tell, I feather gas pedal so when unlocked the rpm will jump around while speed is constant, but locked neither speed or rpm will move with a light touch to the gas. This is my only trick, so some knowledge would be helpful. I have not been driving much this winter.
 

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"Curiously, the manual says you can shift into 4high under 62mph, so might that be TC related? 62 seems awfully high for lockup."

That's referring to the transfer case's "4HI." It has nothing to do with the torque converter.
 

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Discussion Starter #7
There is no connection between TC and the locking hubs.
Of course.
The trans is rigidly connected to the transfer case, which, in 4wd, is rigidly connected to the axles and wheels. The motor is rigidly connected to the wheels (through TC, Transision, transfer case, drive shaft, diff, axle/wheel), so the TC is the only non-rigid connection when the front wheels (4wd) is engaging). With TC locked up then all connections are rigid.
By rigid, I mean mechanically connected as a manual shift would be, not a fluid connection like an unlocked TC would be.
That was the reasoning at the time anyway.
I have figured out that TC locked up well under 62, so can eliminate that as previous post indicate.
I am still trying to know when the TC is locked and why and what conditions it locks, and why it would unlock (aside from very low speed).
When towing up hill I would really like the TC not spinning hundreds of rpm faster than the transmission. It heats up the fluid, and when towing heat is exponential.
It would be nice to find the solenoid wire and get an "on" indicator light when it is locked.
 

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Discussion Starter #9
They dont sell manual used, autos are everywhere, and a used clutch I feel is more likely to be abused than a used auto trans, too few know how to really use a clutch to make it last. I would much prefer a stick...
 

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There is no connection between TC and the locking hubs.
Of course.
The trans is rigidly connected to the transfer case, which, in 4wd, is rigidly connected to the axles and wheels. The motor is rigidly connected to the wheels (through TC, Transision, transfer case, drive shaft, diff, axle/wheel), so the TC is the only non-rigid connection when the front wheels (4wd) is engaging). With TC locked up then all connections are rigid.
By rigid, I mean mechanically connected as a manual shift would be, not a fluid connection like an unlocked TC would be.
That was the reasoning at the time anyway.
I have figured out that TC locked up well under 62, so can eliminate that as previous post indicate.
I am still trying to know when the TC is locked and why and what conditions it locks, and why it would unlock (aside from very low speed).
When towing up hill I would really like the TC not spinning hundreds of rpm faster than the transmission. It heats up the fluid, and when towing heat is exponential.
It would be nice to find the solenoid wire and get an "on" indicator light when it is locked.
your answers are in the FSM, volume TM, section 5AT/AT Control System... but short answer is "its complicated".
Lockup is based on engine load and throttle input. Locks in 4th & 5th. It can lockup as early as 35, but mostly 40mph. Once its locked in 4th, seems to remain locked when shifting into 5th. Have never seen/felt it unlock while in 5th, always downshifts to 4th, then re-lock, then 5th lock.
The more throttle input you give, the longer it will take before it locks up. Once locked, it holds the lock for a long time. There is no 'hard shift point' aside from WOT shift points, and as long as your foot is on the floor, TC doesn't lock and as soon as you back off the throttle it will. If you're concerned about heat generation when towing install a 2nd trans cooler or a even larger trans cooler than stock. Also, keep trans in proper gear so rpms stay mid-range (above 2k) by disabling OD or even shifting to 3rd when climbing. Shifting produces more heat than holding a gear unlocked.
As for the solenoid wire, the TCM is in the trans pan. Its not very likely you'll be able to tap into it. I had a similar hope when I first bought my truck (so I could disable lockup on-demand) but decided it was more trouble than its worth. Easier to get teh right ratio installed so it runs efficiently.
Also of note, itf you were unaware, is that teh TCM is an adaptive/learning trans.
In my opinion Nissan under-geared teh diffs. If they had gone with deeper ratios it wouldn't struggle so much on inclines or towing.
 

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Discussion Starter #11 (Edited)
Thanks, that is helpful.
So, it never locks in 3rd? Only 5th n 4th?
What do you mean, more heat shifting? One shift is more heat than a while unlocked?

One big complaint is going up a hill in 3rd; the engine rpm will jump 900rpm more than the driveshaft (output shaft/transmission) instead of just downshifting. I think it is spinning TC not going to 2nd, because I can see the tach jump up n down if it feather the throttle, n go lower than a 2nd gear could at that speed without shifting back to 3rd, which is not happening that I can tell.
I will take it out of OD when needed to keep rpm high, the trans waits so long to shift down to 4th or to 3rd that I intervene.
313052

I do not, by any means, have a hard-to-pull trailer. It almost disappears behind the truck...
The trans will drop to 1200 or less on an incline when it should downshift. So, which is better, let it lug or spin the TC or downshift for it?
thanks for helping.
 
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