Torque converter enable/disable?

[porcupine73]

OK so I've seen the mod for cutting juice to the duty c to lock front/rear, is it possible with a potentially similar mod to enable/disable the torque converter? I would imagine if you just cut power to the TC lockup when it's supposed to be locked some light would come on like the AT would maybe think it is slipping or something.

[Manarius]

I think that TC lockup is mechanical, not electronic. So, a mod like like that would create some major havoc. Any particular reason you want to kill TC lockup?

[BruceyWV]

I know nasioc people have hotwired the TC to lock up, the drag racing folk. Its just a wire, similar to the duty C solenoid. so I guess if you fed it the current it would unlock.

[johnceggleston]

I know nasioc people have hotwired the TC to lock up, the drag racing folk. Its just a wire, similar to the duty C solenoid. so I guess if you fed it the current it would unlock.

 

what does the TC lock up do? what would the TC unlocked do?

[idosubaru]

if you start tweaking the transmission like this i would highly suggest getting an ATF temperature sensor installed in your ATF line as well and add an aftermarket ATF cooler if needed.

[BruceyWV]

TC Lock up = no slack in the driveline.

Unlocked = slack.

 

It usually only locks in 4th gear cruising on the highway, but it can also on long hills in 3rd.

 

I'll try to find more info from the Nasioc thread.

[porcupine73]

Sounds interesting...I basically want to be able to force it to unlock for that little boost of acceleration when required on the highway without having to shift to third. Yes if you give it the right amount of throttle it will do that by itself but I want to be able to do it myself when I want. I've had other vehicles that had a little button on the shifter that unlocked the TC in top gear (if it was locked).

 

I do have an ATF temp gauge (cyberdyne), a cooler (permacool), and also hydraulic filters.

 

I suppose I could check out the wiring diagrams and give it a try to see what happens. I would guess (hope!) the worst would be the AT light would start flashing or something if it doesn't like it.

[the_postie]

pin 6 on the g/box plug controls the lock up solnoid,up until a 95 model at least ,after that i don't know.

[BruceyWV]

Read away.

 

http://forums.nasioc.com/forums/showthread.php?t=853105&highlight=torque+converter+lock

[nipper]

Before you start fiddling with the transmission you need to read up on the basics, and how the AWD works.

 

A torque converter is a hydraulic coupling unit. Picture two fans face to face one powered one not. The powered fan will move the unpowered one. Simply put a torque converter does this same thing. Locking them up means no lag no slippage. The lockup metohd is a hudraulic piston pushing the TC up against the "housing" (forget what subaru calls it) to make the mechanical connection.

 

Now trying to manually control it will shorten the trannies life, espeically if you are clueless about transmissions. The TC locks up in all gears, being controlled by the TCU. The TC unlocks to avoid shift shock. Shift shock is not only a factor of passenger comfort, but one of the reasons trannies last so long now. This is sometimes done in conjusction with changing the spark parameters in the engine.

 

For the billionth time, the duty c solenoid is part of the equation. There is a spool valve inside the tranny that works along with the duty c solenoid. A majortiy of times when this "wire cutting" is dont by someone with no knowledge of how the tranny works, the AWD unit fails within a year or less. The clucthes in the AWD unit are designed to pulse on and off. They also are made to allow for some slippage for turns. Defeating either one of these without knowing what you are doing is just transmission suicide. Thats a 1000.00 repair.

 

I have no idea why you would want to fiddle with either one since they work fine. iIn almost all conditions the TCU and ECU handle these parimeters very well. I can understand TC LU control for racing. I can understand AWD control for extreem driving conditions.

 

nipper

[nipper]

Sounds interesting...I basically want to be able to force it to unlock for that little boost of acceleration when required on the highway without having to shift to third. Yes if you give it the right amount of throttle it will do that by itself but I want to be able to do it myself when I want. I've had other vehicles that had a little button on the shifter that unlocked the TC in top gear (if it was locked).

 

I do have an ATF temp gauge (cyberdyne), a cooler (permacool), and also hydraulic filters.

 

I suppose I could check out the wiring diagrams and give it a try to see what happens. I would guess (hope!) the worst would be the AT light would start flashing or something if it doesn't like it.

 

UNLOCK!!!!!!!!!!!

:confused:

 

You have no idea how it works at all. If anything you want it to lock to have a direct mechanical connection upon acceleration. The only time it unlocks is to shift, and thats how it operates normally. Unlock is slippage and loss of mechanical power transmission.

 

That little button on other cars was to disable the overdirve or 4th gear. it did NOT disable the lockup torque converter (at least since about 1980's)

 

nipper

[porcupine73]

Hi nipper, thanks for the info. The vehicle I was thinking of with that little button was a '03 explorer but it turns out it had a 5 speed AT (I thought it was 4 spd) so I think you're right the button locked it out of 5th.

 

Well you know how in the Sub when you're cruising along at say 55mph and you give it a little gas and the rpm's jump up a little bit, I'm assuming that's the TC unlocking because if you move the shifter to 3 the rpm's go even higher. I'm also assuming it unlocks the TC there to give you more acceleration b/c the engine just can't pump out a lot of HP at low rpm like that. I just was wondering if I could make it do that manually when I want.

 

I haven't figured why, if the TC locks in all gears, that if I stay in let's say 2nd, anytime you give it a little more gas you can see the rpm's raise up instantly. If the TC were locked then the rpm's would rise only in proportion as the speed started to increase.

[nipper]

The sooby has an honest 4 speed transmission with a lock up torque converter. Putting it in drive three, you are stepping down a gear, not disconnecting the LU TC. (but it does unlock for the shift).

Overriding the TCU for LU TC can cause more harm then good. You can be lugging the engine (i'm sure there is some logic to it that im not privey too). Also in actuality the engine give you faster throttle response and faster incre4ase in speed when it unlocks, to let the torque converter (which multiples torque at amost 3 to 1) do its job. A direct mechanical hook up may take a little more time for the engine to build revs.

Go read up on how a TC works. If you want to feel it work, accelrtae moderatly and dont read the tach. Let your ears do the work. You will hear what sounds like a 1-1.5-2-2.5-3-3,5 shift

That .5 is actually the TC unlocking to allow for the shift. It almost feels like a drop off in power (it is a bit) but it works well. This is part of the reason why transmissions are lasting longer, as they are being enginered to reduce shift shock instead of absorbing it.

 

http://auto.howstuffworks.com/torque-converter.htm

 

Also realize nothing in the drive train acts in a bubble. Everything interacts, so what you may think is actually an improvement can hurt something else (and murphies law at three times the cost).

 

nipper

[firstwagon]

Wow, that's complicated. The auto trans I'm most familular with is the one on my old SkyHawk. Basically a non computer controlled 3 speed with lock up torque converter. The TC lock up on that one had a habit of failing causing it to stay locked and stall the car when you tried to stop at a light. I disconnected the electrical connection on the TC so it would never lock.

 

It really did make the car faster around town. The TC normally locked up very early (max mpg) and was slow to unlock. That meant the low torque 2.0 litre was forced to pull from low rpms. A lot of an automatics performance comes from torque multiplication caused by winding up the torque converter. You don't get that with the TC locked.

 

My opinion would be the idea is sound on older cars but I can't really recommend it on a computer controlled car. You're dealing with an intergrated system instead of an add on part.

[BruceyWV]

Honestly, I wouldnt bother either. Same with the Solenoid C Switch, the system on the phase II 4EAT hasnt let me down once so far, and if it aint broke dont fix it. I just wanted to make sure everyone knew anything was possible

[nipper]

Wow, that's complicated. The auto trans I'm most familular with is the one on my old SkyHawk. Basically a non computer controlled 3 speed with lock up torque converter. The TC lock up on that one had a habit of failing causing it to stay locked and stall the car when you tried to stop at a light. I disconnected the electrical connection on the TC so it would never lock.

 

It really did make the car faster around town. The TC normally locked up very early (max mpg) and was slow to unlock. That meant the low torque 2.0 litre was forced to pull from low rpms. A lot of an automatics performance comes from torque multiplication caused by winding up the torque converter. You don't get that with the TC locked.

 

My opinion would be the idea is sound on older cars but I can't really recommend it on a computer controlled car. You're dealing with an intergrated system instead of an add on part.

 

Early GM LU trannies were a mess. At first they didnt even have a way of turning them off, which made the car a dog. Early failure was common, and the fix is what you described (dad had an olds and we had to do that too).

 

Shift points are complicated. You rally need to see the HP/Torque curves to get a feel for when the trannnies shift and why. I just did a drive and payed attention to the cars shifting. Above 60mph (2500 rpm i think) Press the gas, the rpms and MPH increased at the same time. Below 2500 RPM (60) the car would downshift out of 4th into 3rd. It seems like below 2500 RPM your out of the power band of the car, so you could end up lugging the car staying in a higher gear. What you are blaming the LU TC for is, not the converters fault, but more a factor of the cars power band.

 

nipper

[MountainBiker]

The unlock Porc is talking about is very noticeable when using cruise control. When you hit a hill and the speed drops, the TC unlocks, raising rpm slightly. After quite some time (too long actually) the TCM realizes that speed is still dropping, and THEN it shifts to 3rd. If the hill is slight enough, the shift to 3rd won't ever take place, the TC will just lock again.

[nipper]

a PS

 

TC LU only makes a 150 RPM difference in the tach.

 

nipper

[nipper]

The unlock Porc is talking about is very noticeable when using cruise control. When you hit a hill and the speed drops, the TC unlocks, raising rpm slightly. After quite some time (too long actually) the TCM realizes that speed is still dropping, and THEN it shifts to 3rd. If the hill is slight enough, the shift to 3rd won't ever take place, the TC will just lock again.

 

The cruise control is all f*****d up as far as im concerned. There are times when a gentle squeeze of the throttle is enough, yet subaru chose a program that floors the car instead. This in large part had something to do with mine throwing a rod Now when i use the cruise on rolling hills, i use my foot to squeeze the throttle over the hill to avoid that forced massive downshift.

 

nipper

[MountainBiker]

I agree the CC is awful. But the same thing happens outside of cruise control, regarding the TC unlock. The TCM uses the TC unlock in order to aid acceleration on light throttle inputs. At least in my '02 Forester.

[Wayne Boncyk]

My Outback's CC is no better or worse than on any other car with cruise that I've driven. That said, I can't stand some of this thing's weird behavior - including the massive downshift trick that spelled the end of Nipper's old engine! I always drive with mine in "manual assist CC mode," which basically means I have my thumb always on the CC switch and my foot in the general vicinity of the accel pedal as I'm driving, ready to override - or just shut off - the cruise when I think it's getting ready to do something really stupid.

[nipper]

My Outback's CC is no better or worse than on any other car with cruise that I've driven. That said, I can't stand some of this thing's weird behavior - including the massive downshift trick that spelled the end of Nipper's old engine! I always drive with mine in "manual assist CC mode," which basically means I have my thumb always on the CC switch and my foot in the general vicinity of the accel pedal as I'm driving, ready to override - or just shut off - the cruise when I think it's getting ready to do something really stupid.

 

if it gets really annoying in rolling hills below 70mph ill drive in D3 untill im out of them. That seems to avoid the kamakazi downshift.

 

nipper

[porcupine73]

Yah I think I better just leave it alone, especially after reading in the service manual "LOCK-UP DUTY SOLENOID This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. It then controls the lock-up control valve to provide smooth engagement and disengagement of the lock-up clutch."

 

I just assumed this was an on/off control, but it is not, so slamming it on or off full power is probably not a good idea.

 

I didn't want to make it lockup when it wasn't already, but rather unlock it when it was already locked.

 

Anyway thanks for all the info and suggestions. As always everyone on this board is so kind and helpful!

[Snowman]

Nipper, when did your car chuck a rod? Hope it wasn't in the middle of your big trip. Am I right in assuming that the CC gave it full throttle, causing the tranny to downshift and send the RPMs sky-high?

[nipper]

Nipper, when did your car chuck a rod? Hope it wasn't in the middle of your big trip. Am I right in assuming that the CC gave it full throttle, causing the tranny to downshift and send the RPMs sky-high?

 

Yes it did, going up donner pass, heading home from CA, cruise control gave full throttle, then less then a second later lots of smoke and oil everywhere.

 

Found a great dealership in auburn CA that sold me a rebuilt subaru engine. I paid more then i should have, but i told them if we are going to do this, i dont want to open the hood for 100,000 miles and lets do it right.

 

nipper