The Lockup Solenoid thread for any nissan transmission

[bud]

Okay so as of about awwww 1995 Jatco in japan have been building semi TCU controlled transmissions for nissan to use in pretty much everything from the nissan Cube to the nissan Patrol.

Before 1995 if you were lucky enough to get your hands on a top spec nissan SUV you had an optional switch on the dash that would lock the torque converter up in your selected gear transferring 100% of the power from the engine to the transmission....

As we know you lose about 10% power and 4-8% fuel efficiency due to the fluid friction proccess that is a torque converter.

I am going to write up a thread here and try best to explain how it works and why you should do it.

Firstly the cause and symtoms.

JAtCo transmissions are some of the best there are, smooth changing and reliable if well maintained but there down fall is in there design.
The smooth gear change stems from the ecu allowing the two gears that are involved in this senario...(1st and 2nd) to slip gradually during the proccess the no1 gearshift solenoid will start to release whilst at the same time the No2 Solenoid will start to engage. this in turn releases/applys more gradual pressure to the bands within the sungears involved in this gearshift...end result more slippage= more wear.

Two things are in play here. One is line pressure the other is friction of lack of.

When the transmission is about to change gears the line pressure is dropped by the TCU to allow the smooth change that you should feel.
less line pressure= lack of friction= slipping bands= excessive wear.

The line pressure solenoid is governed by two things a resistor and the TCU.
The resistor is there to measure temperature. IF the oil is too cold it will not allow the lock up solenoid to work and will not allow the line pressure to build up enough. this resistor needs to be changed...this can be done here...

http://www.patrol4x4.com/forum/nissan-patrol-gu-gr-10/line-pressure-solenoid-dropping-resistor-35866/index8.html

Okay onto the switch. In order to get the TCU controlled torque converter to lock up the tcu has to have a certain set of conditions. the oil temp has to be right, the t.p.s(throttle position sensor) has to be within a certain range the C.A.S has to be giving a certain range of rpm's the AFM has to be giving a certain...blah blah blah you get the idea.

how inconvienent it is when towing a trailer up a hill how all of sudden the trans doesn't know if it wants to pick Overdrive 4th 3rd 2nd when most TD/ZD engines torque curves are quite low. nothing worse then mashing the loud pedal and it drops from top gear to 3rd or even second loses all power because now the engine is sitting at the top of its power range.

or how you wish you had a slightly lower gear some where between od and 3rd. or would hold 4th going down hill so you could engine brake without taking the od off and reving the crap out of your TD27.

the answer a DPDT switch.

continued next post.

 

[bud]

Now this switch will do two things when wired correctly.

Position one all is normal
position two bleed line pressure off effectly creating a gear split.
Position three lockup the torque converter as if it was in over drive and

cruising.

position one

pin A is to the line solenoid
pin B is from the TCU lock up signal
pin C is from TCU Line Solenoid signal
pin D is to the Lock up solenoid.

position 2

stops lock up and bleeds line pressure creating split in drive (this won't effect 1st/2nd/rev/

Postion 3

Pin D to the lock up solenoid
Pin C from the TCU line solenoid signal
Pin E to the line solenoid
Pin F +V feed to engage the lock up solenoid

The purpose of this is to reduce the load on the bands with in the transmission and make the torque converter do more work.

secondly, when bleeding the line pressure the transmission oil will get hot. friction from the extra work the torque converter willbe doing as apposed to the bands. ensure you have a good external oil cooler and only use this position for acceleration under heavy load for brief periods of time. ie up hill trailer tow, over taking .

Thirdly ensure the lockup solenoid is disengaged or in its normal operating position when stopping and starting as when locked there is no fluid coupling between the wheels and the engine...it is effectively an manual stuck in gear with no clutch if you try to stop...you will either stall it of bunny hop.

This is where the engine braking effect comes in. as you select a gear and lock the T/C the transmission will not be able to change up or down or coast allowing the engine to absorb the kenetic energy of the vehicle being pushed down hill by gravity...hence engine braking

 

[bud]

You will find the wire's you need to alter in the PDF for your chosen vehicle and also the voltage required to reengage the T/C manually.
ensure you have a fusible link between your introduced power feed and the switch for the lockup.

for most the lockup solenoid wire is the red wire on the 8 pin brown plug next to the fuse box in the engine bay that leads down to the transmission. most jatco transmission have this plug.

To sum it up. the purpose of this switch is to remove the friction from the bands and move it to the fluid, as fluid is easy to cool down the band's not so easy to replace.

 

[firebobby]

You appear know your stuff Bud, but for now, I will stick with a manual box.

 

[solarman216]

I stand corrected bud the T2 Auto does indeed have a lockup clutch, although I have striped a Mistral box I was looking for other problems and just did not notice it, scraped the box in the end as main shaft badly worn so losing too much pressure for box to operate when warm, Rick

 

[solarman216]

Your mods by the way look good to me, but is there not a danger that with people like me who are a little forgetful, of slowing to a stop with the clutch still energised? Rick

 

[cncfabs]

You still can only tow 1800kg legally:doh

 

[bud]

Your mods by the way look good to me, but is there not a danger that with people like me who are a little forgetful, of slowing to a stop with the clutch still energised? Rick

We discussed this issue here on some nz forums and came to the conclusion you could use a momentary switch and a latching relay that was wired via the stop light switch on the brake pedal.. as soon as the brake pedal was depressed the latching relay would release disengaging the lockup.

 

[bud]

You still can only tow 1800kg legally:doh

yeah we won't go there. you guys need to evict your transport minister by the sounds of it.:augie

I built my tow bar, 90x45mm RHS 6 ml end plates 60x60 box section with a 5ml wall and 50x50 for the inner and 12ml plate steel with a 3/4 inch shank tow ball.

haul a tandem axle car trailer with it with the track day car on it. with all the gear and spear tyres , tools etc all up probably close to 5.0 tonne braked all up.

If i was to make anotheri'd make it shorter. my legs have scars now.

 

[cncfabs]

yeah we won't go there. you guys need to evict your transport minister by the sounds of it.:augie

I built my tow bar, 90x45mm RHS 6 ml end plates 60x60 box section with a 5ml wall and 50x50 for the inner and 12ml plate steel with a 3/4 inch shank tow ball.

haul a tandem axle car trailer with it with the track day car on it. with all the gear and spear tyres , tools etc all up probably close to 5.0 tonne braked all up.

If i was to make anotheri'd make it shorter. my legs have scars now.

As a matter of interest what does your chassis plate say maybe your terrano is different to ours.The towing limits are set by the manufacturer not the minister