Torque Converter lock up modification.

[kiwipete]

I have decided to start a new post on this topic. Now I know there is one from years ago on here http://www.nissanpathfinders.net/forum/topic/999-cool-easy-auto-tranny-mod/, but my query has a slightly different twist.

 

This "old" post mentioned cutting the wire to the TC to disable TC lock up, this in turn sends a fault code to the ECU and it then disables further TC lock up when the switch is closed until a reset with the ignition key has been actioned.

What I am proposing to do is have the TC 'lock up" by activation of a switch, and deactivate by another switch (brake pedal). This deactivation is important because the last thing I want to do is stall the engine!

 

There is some input already about this on my "members ride post" http://www.nissanpathfinders.net/forum/topic/22195-kiwipetes-td27/page-17 but I thought I would also post here to get a wider audience and further input on the matter.

 

I have tried the "unlocking" of the TC for towing my caravan (1700kgs) and it works great when in OD and travelling along the highway at 90kph, but the unlocking of the TC causes massive heat to be generated in the TC and I have subsequently destroyed one doing this. I did not think it would have gotten so hot seeing as I have an after market cooler in place. I am currently in the process of ordering a temp gauge for the AT oil and also thinking about getting a larger cooler too.

 

With much toing and frowing I have settled on the following circuit, unless I find something better

.

I propose to use this circuit to "lock" the TC when in D by way of another relay being supplied by a diode from the D switch on the gear lever selector. My reason is that this would be a fool proof way of ensuring I do not accidentally press the "activation" switch and enable the TC lock up when in P, N, R 1 or 2

 

What I need is further input to see if this is indeed a viable way of achieving manual lock up of the TC when needed?

 

It has been suggested to me that I simply drive it in D when towing on the highway, but at 90kph and pulling 3500rpm and being a diesel, revs = noise and almost zero acceleration.

 

 

 

 

[Precise1]

I'll be watching this with interest. Sorry, I can't help with the circuitry, I'm an idiot when it comes to electrons...

 

 

I am currently in the process of ordering a temp gauge for the AT oil and also thinking about getting a larger cooler too.

Absolutely to the first part, I'm surprised you don't have one already considering all the other goodies you have. A second cooler might be a good idea rather than just a larger one. I know you can set up a T with a thermal switch to only use the second cooler when appropriate.

 

Did you ever install the little air gauge? I can't recall...

 

B

[kiwipete]

The air gauge is still on the "to do" list when I redo the on-board air system.

[kiwipete]

I have revised my schematic drawing to show the trigger relay, this is to be powered by the sense wires from the gear selector switch.

 

I have not yet tested this diagram, but will do so just as soon as I have enough parts available.

[92Path_68CJ]

Just a thought on the transmission cooler, maybe go with a better cooler, and add an electric fan on a switch to help keep it cool?

 

I've seen small fans for trans coolers before.

Edited February 8, 2014 by 92Path_68CJ

[Nefarious]

Do you intentionally have some of those diodes reverse biased? I can help u with a wiring diagram, but need to know the conditions for the t/c to lock up.

 

What signal is sent where to actuate the lock up?

 

You have the led reverse biased, but the gear selector switches diodes are forward biased.

 

The cathode of the LED should be to ground or you will fry it. Standard diodes will block DC below breakover voltage, but the LED is not designed to block voltage. It will fry.

 

Post up some specifics on what conditions u need met and what signal needs to go where to actuate lockup and I can probably help you out.

[kiwipete]

Do you intentionally have some of those diodes reverse biased? I can help u with a wiring diagram, but need to know the conditions for the t/c to lock up.

 

What signal is sent where to actuate the lock up?

 

You have the led reverse biased, but the gear selector switches diodes are forward biased.

 

The cathode of the LED should be to ground or you will fry it. Standard diodes will block DC below breakover voltage, but the LED is not designed to block voltage. It will fry.

 

Post up some specifics on what conditions u need met and what signal needs to go where to actuate lockup and I can probably help you out.

 

Yes you are right about the LED, it was a quick slap up drawing, sorry.

 

The diodes for 2 D and OD are to allow voltage to travel through the relay only, prevent voltage going back to the other selector wires.

The same for the other two diodes, I only want the voltage to flow through to the T/C. The way I see it the ECU can supply 12V to the ECU at any time it likes, but with the relays there I can manually supply 12V to it too without the 12V I supply going back to the ECU. Does that make sense?

[kiwipete]

Just a thought on the transmission cooler, maybe go with a better cooler, and add an electric fan on a switch to help keep it cool?

 

I've seen small fans for trans coolers before.

 

Yes I thought about a cooler with a fan too but I am not sure there is clearance for the fan between the cooler and the grille. Another thing I would have to be most careful about with the fan is remembering to turn it off should I be going through any water. Be a bugger to have the blades go through the core.

[92Path_68CJ]

 

Yes I thought about a cooler with a fan too but I am not sure there is clearance for the fan between the cooler and the grille. Another thing I would have to be most careful about with the fan is remembering to turn it off should I be going through any water. Be a bugger to have the blades go through the core.

 

Good point! On my next rig I might try to relocate the cooler so I can use a fan.

I overheated my last one too many times. The cooler I could fit with the bigger radiator wasn't enough to keep it cool on steep mountain roads. I'm sure you'll have way better luck, you know way more than I did then.

 

[slide]

Just noticed this thread, have just posted this on kiwipetes build thread, but I'll post here as it will be easier for others to find.

 

I haven't tried this, but this is how I see it working;

-The ECU controls Torque Convertor when not locked by relay (diodes stopping backfeeding power)

-when mom-on switch is pushed it powers up pin 85, activating windings inside relay, which are earthed through brake lights bulbs (86)

-windings move relay contact, putting power to terminal 87

-power flows through (green) diode, keeping power to terminal 85 (and thus holding itself activated)

-when brakes operated power is put to pin 86

-when pin 86 and 85 both have power, no current flows so relay deenergises, removing power from pin 87

-when pin 87 has no power TC convertor operation returns to ECU controlled.

- a pilot light could be wired to pin 87 to know when circuit is operational, or to wire to torque converter to know when its locked (both ecu and relay locking)

-could get fancy and have both, or even a two colour LED

 

Anyone have any feedback?

Nath

[kiwipete]

I think you are on to something here Nath,

You are a master of all things electrical I had not gotten around to testing my theories with a dummy set up, but will try to get out to the workshop today and test your theory.

I think I have enough parts available to give it a try.

I like the idea of a dual colour LED to indicate the state of the TC too.

[kiwipete]

Nath, I have tried this circuit on the test bench and it does in fact work, many thanks indeed.

 

All I need to sort out now is the trigger input section where a feed from the 2 D or OD switch sense wires allows the above circuit of yours to be activated. I just do not want to have the manual over ride of the TC to happen any old time.

[slide]

Nath, I have tried this circuit on the test bench and it does in fact work, many thanks indeed.

 

All I need to sort out now is the trigger input section where a feed from the 2 D or OD switch sense wires allows the above circuit of yours to be activated. I just do not want to have the manual over ride of the TC to happen any old time.

 

Awesome! Great to know my theorys pretty bang on :-)

What have you used for diodes? (obviously diodes, but where did you get them?)

 

Does your dash display have the P-R-N-D-2-1 illuminated to indicate lever position? Damn, I was thinking of using these to trigger relay, but as I typed I realised that wouldn't be ideal. As even tho gearstick is in "D" doesn't mean the trans stays in 3rd, it will switch between 1-3(&4th with od button pushed). Maybe the ECU has some signal to (or from) it so it knows what ratio its in? Need to study the wiring diagram for this info I imagine

[kiwipete]

 

Awesome! Great to know my theorys pretty bang on :-)

What have you used for diodes? (obviously diodes, but where did you get them?)

 

Does your dash display have the P-R-N-D-2-1 illuminated to indicate lever position? Damn, I was thinking of using these to trigger relay, but as I typed I realised that wouldn't be ideal. As even tho gearstick is in "D" doesn't mean the trans stays in 3rd, it will switch between 1-3(&4th with od button pushed). Maybe the ECU has some signal to (or from) it so it knows what ratio its in? Need to study the wiring diagram for this info I imagine

 

I just used a small IN4001 diode for the test bench layout but I will get some power diodes from our local electronic parts store. http://www.jaycar.co.nz/products_uploaded/p600a.pdf

 

Thanks for the insite too as I was thinking just going to go off the gear selector switches for the signals. 1st gear when in D probably would only be selected after braking therefore disabling the circuit? Still no harm in looking further into this all the same.

 

Thanks for the input.

[kiwipete]

I have had a further tinker with the simple latching relay circuit to energise the "solenoid lockup" from a momentary push button switch, and de-energise with the break pedal circuit.

It works on paper.


And here it is on the bench.


Left switch and right lamp mimics the "lockup button" energised


Right switch and left lamp mimics the "brake switch" energised


Right lamp (lockup) energised via white lead connected to 12V as it would be when powered by ECU


I am toying with a similar circuit to this that will be used to fool the ECU when the TC is open circuited as per the start of this post. This would involve a resistance so the ECU still thinks the TC is in circuit, thus no error codes.

I have a little experimenting to do first.

[Precise1]

*waits patiently*

 

B

[SpecialWarr]

You lost me at diode.

 

sent from under Ernest the Pathfinder

 

 

[MY1PATH]

On 4/6/2014 at 9:48 AM, Precise1 said:

*waits patiently*

 

B

Did you forget that you were waiting? I sure did!

On 4/5/2014 at 10:47 PM, kiwipete said:

I am toying with a similar circuit to this that will be used to fool the ECU when the TC is open circuited as per the start of this post. This would involve a resistance so the ECU still thinks the TC is in circuit, thus no error codes.

I have a little experimenting to do first.

Fooling the ECU is easy, I just did it this weekend. I believe the ECU is simply looking for continuity so any resistance should do.
1) After I went to bigger tires, I placed a simple on/off switch between the TCU and the Lock Up solenoid too keep it unlocked at low speeds. This worked great until I got on the highway and the TCU won't re-enable Lock up because open circuit triggers a code and disables lock up. 

2) I made a dummy circuit between the TCU and ground to close the circuit. This is comprised of a 130 ohm resistor and an LED. Its always connected regardless of my switch position so there's never any break in continuity when I flip the switch. Now I have zero issues turning it back on when I get on the highway. A few things to take note of:

-TC unlocked is 1v so LED is dim when TCU is not sending lock up.
-TC locked is battery voltage so LED gets brighter when TCU is sending lock up.
-The TC solenoid is 10-16ohms and my dummy circuit is about 10x as many ohms. There is zero concern of my dummy circuit robing any current for the solenoid's proper operation.

Edited June 24, 2022 by MY1PATH

[Precise1]

On 6/23/2022 at 5:06 PM, MY1PATH said:

Did you forget that you were waiting? I sure did!

Yes.

 

I've since gotten an electronics education (trade level), so that actually makes sense to me.

Good job, and good timing.

 

B

[shanee11]

thanks for the update on this very annoying aspect of our auto trans..

MY1PATH have you got any pics of wiring or a diagram of were you installed wires..

im not 100 percent up on auto elec stuff.

i have tried all the same actions as others but this sounds neat and easy to install.

thanks heaps ,,

shane.

[MY1PATH]

On 6/23/2022 at 5:06 PM, MY1PATH said:

 Now I have zero issues turning it back on when I get on the highway. A few things to take note of:

-TC unlocked is 1v so LED is dim when TCU is not sending lock up.
-TC locked is battery voltage so LED gets brighter when TCU is sending lock up.
-The TC solenoid is 10-16ohms and my dummy circuit is about 10x as many ohms. There is zero concern of my dummy circuit robing any current for the solenoid's proper operation.

I was wrong, It does not like prolonged operation, I guess my next attempt will be to match the ohms of the TC solenoid and see if that does better. Or it could be something like a rev counter or pressure sensor triggering an error after a certain amount of time with the TC off... 

I'm out of country for a while so I will not be messing with it until 2024-ish. At that time, I might look into aftermarket TCU that I can program and forget about instead running extra switches to get around factory programming. That will enable multiple lockups (4 speed to act like a 6 or 7 speed) and no lockups to occur below 1600 RPM (to cut down on the smoke)

 

On 3/12/2023 at 4:01 AM, shanee11 said:

thanks for the update on this very annoying aspect of our auto trans..

MY1PATH have you got any pics of wiring or a diagram of were you installed wires..

Everything's different on the the RHD diesel. Nothing matches the vg30 FSM's I have.
The TD27 FSM info I have is either wrong, year, incomplete or non-existent so I don't get easy answers either.

Edited March 15, 2023 by MY1PATH

[adamzan]

Glad to see you're still around, Garrett!

[92Path_68CJ]

Its been years since I've been on here but I still wonder about this from time to time, I'm curious to see what the solution ends up being.