Controlling torque converter lockup 2

[rikakiah]

Ok, I'm probably over my head here as I doubt I'm as technical as many of you, but here goes...

Is there a way to directly control when the coverter locks up (I'm assuming by way of the torque converter clutch circuit?)? For example, for a car (Ford, if it matters) that normally only locks up in 4th, is there a way to apply voltage (or remove voltage) from the TCC circuit in order to force lockup in say 3rd or even 2nd? Any specifics would be appreciated. And yes, I realize this is only a limited application deal as I'm sure continual lockup isn't good for tranny longevity.
Thanks

 

[rikakiah]

Oh, one other thing: failing the above circuit, would there at least be a way to tap an LED into the TCC circuit (assuming I'm on the right track there) to at least tell exactly when the converter is locked up?

 

[GregLocock]

Well that is an interesting question. If you are in Australia, and you have an EB-EL, then the answer is yes, it is possible to directly control the lock up clutch with a switch. If you get hold of the proper workshop manual you should be able to figure out which wire needs to be intercepted. The easiest acceptable relevant plug is a round multipin squashed between the cylinder head and the firewall.

The trouble is, when you activate the LU clutch the electronics will detect a fault condition and drop you into third gear, where your car will stay (if you are in Drive) until you reboot the ECU.

Yes, it is easy to fit an LED on that line so you can see when it is locked, if you can't tell by ear.

Incidentally if you select 3 then it will hold 3rd locked as long as humanly possible, it is designed to be a very good towing gear.



Cheers

Greg Locock

 

[Metalguy]

Dunno about Fords, but I rigged up TWO switches on my GM 4T60 trans. One controls the TCC, the other makes the trans go into OD (4th).

The TCC in these trans. releases every time you let up on the gas (return to idle)-someone in GM apparently decided that in a panic-stop, it's better to unlock the TCC early. I guess some lawyer managed to win a case against GM or something, so too bad about early TCC failure caused by a few extra thousand clutch applies every year or so. With the TCC switch "on", it stays locked up. If the engine is at ldle (coasting), after about 5 sec. the computer makes the "check engine" light go on, but that's all it does. It stays lit until the next restart.

Ah well, light bulbs are cheaper than clutches.

 

[rikakiah]

You guys are awesome. I think for now, I'm just going to hook up an LED for fun to see exactly when it's locking up. However, I'm still considering the control idea once I know more about what's going on. The car is an Escort ZX2. I was told that the tc only locks up in 4th on these cars. I don't feel anything in third (at least not when I use D to hold it in 3rd and when in OD, it always shifts to 4th too soon). I'm mainly looking for fuel economy when cruising, but also just kind of have the urge to mess with it since I heard I can...

 

[GregLocock]

The trick to finding if the LUC works in 3rd (other than fitting a LED, which is a great hack) is to accelerate slightly one you are in 3rd, then back off gently, you should hear the revs suddenly drop as the LU clutch engages. Then feed in more throttle until it releases. Do this for several speeds and note the two throttle positions (if you have a throttle position sensor or vacuum gauge) and you have part of the trans strategy mapped.

Cheers

Greg Locock

 

[Andy330hp]

I wired the lockup on my 700-R4 directly through a lighted switch, so no need for the additional LED (until the bulb burned out. doh!)

Oh, I also wired mine through the brake switch, I don't know if it is causing premature wear or not, I was just following the advice of others on that one.

It will lock in 2nd, 3rd, and 4th gears. The switch is kind of a pain in the butt, if you forget about it when you come to a stop light, then pull away, the instant you hit second the converter locks and pulls the engine waay down! A better solution is a vacuum switch/4th gear switch

I think Painless has a diagram on their website for both techniques.

 

[Pancholin]

I would suggest going to some of the diesel sites. Banks engineering has an exhaust brake that requires a TCC lockup switch to be effective. I got tired of needing the brakes to descend grades with my 93 Chev 6.5 diesel and put a DPST switch in a handy place to reach and use it without problem at all. When I forget to switch it off it reminds me when shifting from first to second.
Pancholin

 

[JayMaechtlen]

Maybe a job for a Basic Stamp or the similar?
Just a bit of logic and a few inputs- only one output.



Jay Maechtlen

 

[Andy330hp]

The wiring is very simple. The device that controls converter lockup is just a solenoid. You'll be able to trace the two wires whe you rebuild it to figure out which two pins in the 4-pin connector that you'll need. Then, give one pin +12ignition (hot in run or start). I suppose you could go constant hot, but there's no real good reason to do so, and a couple reasons not to. Run the ground first through a brake switch (just about any car or truck in a junkyard that had a 700 will have one), then through a lighted SPST dash switch (electronics store), then to ground. Something else that is recommended is a vacuum switch. This is also very easy to find in the yards. I know for a fact some early 80's trucks have them, and pretty much any car that had a 700 but WASN'T EFI will have one. Since this will be mounted in the engine bay, it will probably be easiest to pull your +12 from the coil, then go to the vacuum switch, then to the trans

 

[Smith231]

Are there any risks for (besides decreased fuel economy)in the case where voltage is applied directly to the torque converter control solenoid in order to unlock the torque converter lock-up? Will switch unlocking it cause any damage to other components? This would be in the case where the hydraulic control valve is faulty causing intermittent lock-up and vehicle surging at high temps. Specifically, this is for a Buick Lesabre.

 

[Metalguy]

IIRC, you apply 12v in order to apply the clutch, not release it. Preventing it from applying will add heat to the trans.

A much better way to go, especially if your problem doesn't occur at low-mod. trans. oil temp., is to add a trans. oil cooler ahead of the radiator/AC condenser to remove some heat.

You can also use a slightly thicker ATF from Red Line, because this problem USUALLY involves the oil getting too thin, so the valve-body valve leaks a bit more than what the "designer" thought it would.

It's a very common problem with these trans; starts around 50,000 miles.

 

[Smith231]

Thanks for the input. I did install a transmission cooler; the largest I could fit in, about 11"X11" (3/4" thickness). It helped considerably. The engine temp is quite a bit cooler too.

I'll check into the Redline fluid. Prior to the transmission cooler, it would surge when the outside air temp was greater than 75 degrees, after about 20 minutes of highway driving. With the transmission cooler, it typically only surges after approximately 20 minutes of highway driving, when the outside air temp is at least 92 degrees.

At cruising speeds, it is fine. Climbing slight grades, under load is when it really lopes. I manually switch off the torque converter lock-in for the hills. I wired a test light to the solenoid circut. At idle, the light is on; when locked in, the light is off. The transmission must come out of this car to access the valve body. Thanks.

 

[Metalguy]

Hold it! The problem I described affects steady crusing too. It isn't load-dependent, which is what you describe. Your trans. computer may simply be sensing low engine output (low vacuum, air intake valve opened pretty far, etc).

 

[Smith231]

I have heard that there is a hydraulic pressure test that can be performed to confirm or disprove a faulty regulator valve in the valve body. If it is the regulator valve, the hydraulic pressure should change when the surging takes place. There is a vacuum modulator on the transmission, but I don't think those go bad too often. It may be a problem that results due to to heat and vacuum loss. I have searched for leaks previously though. The torque converter will lock-in around 30 mph hour in the car. I noticed this when I had the test light attached. From what I have read, it should lock in at a minimum speed of about 45 mph. It usually happens right after shifting into high gear (1500 to 1800 RPMS) and then clears up at cruising speed. It returns on hills under load (a steady lope). It seems to happen on curves as well, like on entrance or exit ramps. There are no codes and the torque converter clutch circuit is functioning properly.

 

[Metalguy]

Hopefully this isn't a case where the trans. fluid level is a bit low.

 

[Smith231]

Trans fluid level is fine. I changed the fluid and filter about 18,000 miles ago. The old fluid looked fine and the pan was clean. No leaks either. It shifts on time and very smooth. The only exception is when it starts surging after locking-in. This happens until I hit cruising speed. If I flip the switch it clears up though. If I feather the accelerator pedal, it seems to clear it up (or get it through it faster.

 

[jetmech]

Smith321, I have a problem that seems similar to the one you are experiencing. On my wifes 1997 Pontiac Bonneville at torque converter lock-up it shudders under a slight load. This will happen when in lock-up and a slight load is applied, such as going up a small grade. This also only seems to happen once warmed up, after driving for about an hour. I prefer not to band aid it with a cooler, but repair the defect. I was thinking that the lock up clutch may be worn. Checked for codes and there were none. Any information would be greatly appreciated.

 

[Smith231]

There is a regualator valve inside of the valve body in the tranmission. Unfortunately, the transmission in this car must come out to get the valve body out. The way I understand it is, when the transmission and the fluid get good and hot, the fluid becomes thinner and there are rubber seals in the regulator valve that expand somewhat, allowing fluid to escape during lock-up. Consequently, it doesn't want to stay locked-in continuously, because it just can't quite maintain the hydraulic pressure required for lock-up. This type of problem will not generate a code. If the lock-up circuit were faulty, a code would be stored. If a transmission shop pulls it, they will probably want to rebuild the whole transmission, especially if it has some miles on it. That will probably run about $2000. Your problem does sound more like a torque converter problem because a shudder is more indicative of a torque converter. Mine is more of a surge, so it could be a vacuum problem. A transmission shop will probably diagnose your problem for free. There is a way to monitor the hydraulic pressure to help determine if lock-up is not being maintained. Also, I have heard that there could be a weak spring in the valve that could cause a similar problem. If it is taken out, a rebuild is probably the best way to go to make sure it is fixed.

 

[Metalguy]

I believe Trans-Go in CA has a converter-clutch valve kit that eliminates the problem, but I don't think it can be installed w/o pulling the trans.