Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

What happens if I remove the wire to the TCC solenoid?

I have a 1993 pontiac sunbird 4.0 LE engine. I was told by a repair shop that my throttle converter clutch solenoid (TCC solenoid) is bad.

I have read that you can unplug the wire to it, and it will not harm the car, but I will use more gasoline.

If I do this, is it going to harm my car otherwise.

Thanks, JR

Nope. Won’t harm a thing. You just lose the lock up torque converter function which will reduce fuel mileage.

If the TCC solenoid is sticking causing the engine to stall at idle, you might try this. Purchase a can of SeaFoam TransTune and add a half a can to the transmission fluid. I’ve had good luck unsticking TCC solenoids using the SeaFoam.


Transman says that if you disconnect the TCC you will cause the transmissin to overheat, due to the constant slipping of the converter. I have never bought that assunption and the gas mileage will not suffer much because the converter doesn’t lock up anyway until you reach cruising speed, and most cars would perform better if it didn’t. Most cars don’t have enough power to run in “lockup” without “unlocking” on a hill and “locking up” again when it levels out. My old Dodge not only “unlocks” on a hill but downshifts to 3rd gear at the same time, which I don’t like.

The car only does this when we slow down to stop. (more often after we have gotten off the highway) It starts vibrating, shaking, ect really bad, then dies once we have almost come to a complete stop, and the brake petal gets hard to push. Then we try to start it, it runs, until we put it into gear, then it dies again. Once we have let it sit for awhile, it will go again.
Like I said we took it into a dealer repair shop and they said it was a bad TCC solenoid, and would cost the over $600 to replace the solenoid.
After reading the internet it shows that the part can be replaced just by removing the transmission pan. The dealer says that they have to remove engine bolts, the transmission, ect to get to it. We dont want to try to fix it ourselves until we know where it is exactly. I have not been able to find that info out just yet.
I did read that you can simply unhook the wire to the solenoid, but it would cause the car to use more gasoline.
Is there anyway to find out for sure where that is located? We have a book on the car, but it does not show the location.
If I add that seafoam cleaner, do it matter how much I use for my car? It wont hurt adding it if the fluid is already full?
I would like to try something like that first. Then if that doesnt work, I could try unhooking the wire to the solenoid. My car has over 204.000 miles, so its not like it has long to live anyway. But then I have seen several sunbirds at Pull A Part that have at least 250.000 on them.
I just didnt want to unhook it and have it cause more problems.
Thanks again, JR

Trans will not overheat due to constant slipping of the converter. They do that constantly in city driving anyway. Could 100,000 cabs be wrong? The lockup is only for steady driving and does save about 3-6% when you are at steady speed. Otherwise it disengages and reengages all the time usually from 30-40 mph. like city driving. The trans are built to handle the stop and go so turning it off is not a problem.

DO NOT just disconnect it and leave it at that. The Lockup solenoid is under the side cover. Sometimes the engine cradle needs to be lowered to get the side pan off. The solenoid is around $50. Dont go to a dealer, take it to a trans shop. $600 is WAY too much to pay for this. Disconnecting the lockup solenoid will not only cause a loss of MPG but it will cause the transmission to run much hotter and depending on how hot your trans is running normally it can most definately cause the transmission to overheat. Dont chance that with a trans which has over 200k on it. We’re talking about a $50 part here. This $50 part has the potential to cost you over $1000. If you have any questions about this, ask a pro.


Does anyone know if there is a diagram anywhere on the internet showing exactly where the solenoid is located?
Also any idea where to purchase this TCC solenoid? I have tired and tried looking on the internet, and cannot find any web sites that have one.

Thanks again!

Right behind the drivers side front wheel you will see a transmission pan mounted sideways. Remove this pan and the lockup solenoid will be behind there. Easy to replace. Look at it real good, on your vehicle you just might be able to get that cover off without lowering the engine cradle.

Here is a pic of the lockup solenoid. Check with your local auto parts stores, they might carry them. I was wrong about the price of yours, my supplier LISTS them for $35 so you should find them for under $50.


Back in the day, there was no such thing as locking TC. But, the systems were built a bit more robust back then, esp cooling systems, to handle the additional heat. I have no doubt some systems today are built more marginally and therefore susceptible to overheat.

Back in the early 90s I bought an '89 2500 w/thrashed 700R4. The fluid was wasted, brown and the trans was having trouble. I did a fluid swap and unplugged the TCC. It was intended as a beater plow truck for me anyway. I ended up running that truck almost daily to work (30 miles one way), plowing and general hauling duties like that for a decade.

I used it to haul my plow, all my welding/gas tanks, engine blocks, a car trailer with a vintage vette and other assorted gear on it, from the WI to MA. I was afraid I’d get pulled over for being seriously overloaded. I sold the truck a few years later and it’s still going strong- TCC disconnected. YMMV.

Yeah, cooling systems aren’t buffered like they used to be. Around town the electric fan typically provides air flow that would not otherwise be possible at a given engine rpm.

Side note on interesting trans cooling modalities: One Toyota pickup with HD trans cooler (I assume it’s a Tundra) ONLY engages the air:fluid auxiliary rad up front when the converter is unlocked. When in lockup the system reverts to engine coolant fed directly from (something like) the heater circuit locally at the trans. No in rad cooler tank at all. One thermostat controls both engine and trans. It’s very much like the sandwich laminar coolers found on some 80’s Fords and many Euro’s through today.

The only true advantage I see for the lockup converter (other than eliminating unnecessary heat) is that it can allow a really high stall converter to compensate for lower powered engines without paying on the other end. Otherwise, just throw in higher gearing for economy’s sake. It may not deliver quite as much drivability …but …SO?

I often thought a trans composed of a series of converters with lockups would be more reliable than the CV transmissions. Virtually unlimited torque and low losses at cruise.

Unplugging the torque converter clutch will not harm the transmission or cause it to overheat. This is just a regular three speed automatic transmission with the TCC lock up feature. When the TCC solenoid is unplugged it reverts the transmission back into a regular automatic three speed. How long did we have three speed automatic transmissions before they added the TCC feature? Those transmissions never overheated because they didn’t have the TCC feature.

When the SeaFoam didn’t free up the TCC solenoid, I would unplug the TCC solenoid to prevent the stalling problem. And people drove their vehicles for years with the TCC solenoid unplugged with no tranny problems.


When shopping for parts, be sure to ask for: “TORQUE Converter Control Solenoid”, or “Transmission Control Solenoid”, or “Torque Converter Clutch Lock-up Solenoid”.
[ I’m glad the parts suppliers (almost) made their minds up on a common name for this part !]

WHAT is the size of that engine? Is it 2.0L, or 3.1L? I don’t find an other size.

It doesnt matter whether you “Buy” anything or not. Facts is facts whether you like it or not.

Fact 1: Torque converters generate lots of heat from slippage.
Fact 2: Torque converters are designed to dissapate heat (During the non lockup time under 40 mph) This is your 100,000 cabs issue.
Fact 3: When lockup ocurrs, the converters pump and turbine are coupled resulting in no slippage. No slippage = no more heat. This is when the converter cools.
Now, lets unplug that lockup solenoid. What happens?? The pump and turbine are no longer coupled and the slipping begins. Well, who can drive 40 mph or less, not me. Get on the expressway, get up to 60, 70, 75… With no more lockup, the converter clutch is slipping its life away at high speed. Since the converter is not designed to dissapate that much heat at one time it starts to balloon, then it turns blue, then it fails internally.
Now, Mr Ellis, if you still think I’m wrong here, I would love to hear it. I have been explaining this to you for some time now and I’m trying to put it as simple as I can since you are not a mechanic. Please make a point and back it up with a link or two for us to look at. I’m providing links for you to back up what I say.

Now, Twin turbo, I’ll bet that HD 2500 had a HD cooling system in it which would definately help keep the converter cool.


I realized last night when I was going to sleep that I posted I had a 4.0 engine. Its a 2.0. Sorry about that. I have been so stressed over this car thing, and then spent the day yesterday on the internet trying to find out all this info, I just wasnt thinking right.
I just called a local tranny parts store, and they said it would be $20.39! How about that. Sounds cheap.
Now to get it done! LOL
Thanks again, JR

Wow, good deal. Dont forget the side cover gasket, its only a couple of bucks.


Well, Transman, it seems that a few others disagree with you. With your Idea one wold burn up a transmission if they drove around town under lockup speed. Slipping oil doesn’t generate much heat. Here are a couple of quotes from the links you provided " Highway vehicles generally use lower stall torque converters to limit heat production, and provide a more firm feeling to the vehicle’s characteristics" “In modern designs, the blade geometry minimizes oil velocity at low pump speeds, which allows the turbine to be stalled for long periods with little danger of overheating.”

Well I called a couple of transmission repair shops, and got quotes from $225 to $350 for them to do the work, including the cost of the part.
We can do the work ourselves, but at that price, we might just have someone else do it. My biggest decision is to find one that has a good reputation. Is that possible? LOL. There has to be some out there that are honest.
I still might just pull the wires, and drive it like that. Since it has over 204.000 miles, I dont know how long its going to last anyway. While money is tight right now, I would like to just pull the wires, and it looks like after reading these posts, it should be ok, I just think I might be better off having the work done, and overwith.
Thanks again, JR

Re read what I said, in fact never mind, I’ll post it here again for you. “Get on the expressway, get up to 60, 70, 75… With no more lockup, the converter clutch is slipping its life away at high speed. Since the converter is not designed to dissapate that much heat at one time it starts to balloon, then it turns blue, then it fails internally.” There is nothing in my post referring to overheating around town. In fact it states that converters are capable of dissapating heat at pre lockup speed. Every link I posted supports my statements. You state that highway vehicles use lower stall converters to reduce heat. We are not talking about lower stall converters. And we’re not talking about vortex flow. We are talking about heat being generated by disconnecting the converter clutch and driving with it disconnected. I stand by my statements.


Thats entirely up to you, just as long as you are aware of what can happen by leaving the solenoid disconnected. When you called those transmission shops did you happen to ask them about what could happen by driving with the solenoid disconnected?? The $225-$350 is much more in the ball park than that $600 quote you got.
As far as trans shops go the small mom and pop type of shop will do you much better than those large chain type shops.

Good luck with it.


“Mom” is the mechanic. “Pop” is the counter person.