Transmission Problem (TCC)

I have a 1997 Buick Lesabre Custom that has approximately 118,000 miles on it. Since I bought the car, I have been struggling to figure out a “chuggle” or “fishbite” issue I have been having on light acceleration up mild grade hills. With constant acceleration going up a low to mild grade hill, the engine will stutter, almost like a misfire, then the tachometer will drop to about 1100 RPM’s (from 2000-3000 RPM’s). Also, under the same conditions, the engine will begin to surge/fade. If I hold the gas pedal in a constant position when the “chuggle” occurs, sometimes, the tachometer will begin to climb/fall around 500 RPM’s repetitively. The result is the car lurching forward and backwards, which is a very annoying drivability issue.

If I take the car onto the highway, the CEL will come on during a longer trip ( > 10 miles). I will post the DTC when I find where I wrote it down, but it does reference the torque converter clutch in the transmission. I also have an issue braking from high speeds (around 40 MPH or higher) going down a steep hill, the entire car will shudder violently while the brakes are applied.

I have opened other topics regarding this issue and several other problems I have had with the car. All other problems have already been resolved, but this issue still remains. So far, this is what I have done to fix the car up:

New plugs/wires
Coolant flush
New water pump, upper/lower radiator hoses
New fuel pump/sending unit/fuel filter
New front brakes/resurfaced rotors/tires
New idle air control valve
Cleaned mass air flow sensor
Changed upper-intake manifold and lower intake manifold gaskets
New PCV valve/air filter
New manifold absolute pressure sensor (MAP)
2 new oxygen sensors
New fuel pressure regulator

As far as I can tell, all of the drivability issues I am experiencing can be linked to the TCC. I assume the TCC is slipping, which can be caused by a large number of internal transmission problems. But, other than these 3 issues, I have absolutely no other transmission problems. It looks like the TCC is a common problem in GM transmissions. Any type of professional transmission work is not an option due to limited funds.

I have changed the transmission fluid/filter twice in the past six months – the fluid never looked or smelled burned and I never found any metal shavings in the pan. The car currently has Dexron VI and everything appears to be in good condition.

I read that the TCC can safely be disconnected from the transmission (sacrificing minimal gas mileage) which would eliminate all of my drivability problems. The difference in MPG is most evident on the highway, but the majority of my driving is city anyway. So, I am trying to find a way to prevent the TCC from engaging, ever, and accept the loss in gas mileage.
I found the wiring diagram for the “transaxle” for my car from ARRC. It holds the following components:

TCC Enable Solenoid (TAN/BLK)
TCC (PWM) Solenoid (BRN)
Shift Solenoid A (LT GRN)
Shift Solenoid B (YEL/BLK)
Transmission Fluid Temperature Sensor (BLK and YEL/BLK)

There is also a PINK wire (ground, I assume) for a total of 7 wires listed. I checked briefly under the hood and found 1 wiring harness on the transmission. Facing the windshield, the connector was on the top of the transmission, on the right hand (driver) side of the car – near the coolant temperature sensor. The connector is round and has 6 wires. The wire colors are extremely difficult to define – they are very dirty and all look relatively dark/black.

I read somewhere on these forums about Smith1000 hooking up a toggle switch from the cabin to the transmission connector – from what I understand the TCC wire has a constant 12V to keep the TCC off, and the 12V is removed to engage the TCC. So, the switch allows the driver to change between applying constant 12V to keep the TCC off and the normal TCC wire for default operation.

This solution is exactly what I am looking for! I could not care less about a CEL; as long as the drivability issues are resolved I would be happy. I do have a few questions:

1. Does leaving the TCC disabled permanently cause any damage to the transmission?
2. What type of drop in MPG should I expect?
3. Do I have the correct wiring harness?
4. Does anyone have the pin-out for the wiring harness?
5. Does the TCC wire have 12V applied with the key in the on position?
6. What color should the wire be?

I can easily check the wiring connector with a voltmeter to find which wire has a constant 12V applied at idle – can someone please confirm that no other wires on the connector have the same behavior?

Thanks in advance for any help; I am hoping to finally resolve this nagging annoyance!

You have done some great research. I did this years ago and still use a toggle switch to throw out the tcc in my '97 Lesabre, when the car has the fishbite. It usually happens during fairly warm weather. From what I recall, it requires 12 volts to disengage the tcc, or to lock it out. I cut the brown/blk wire on the tranaxle. Leaning into the car looking down (facing the car from the front), it is the top wire on the right coming out of the transaxle wiring harness. I added wire and looped through the cab to a toggle switch. The wire loops back out and reconnects to the other end of the cut wire. I ran a 12v source to the "on" position on the toggle switch. The wire simply loop through the cab switch, but when it "bites", flip the switch on and it feeds 12V to the tcc, which holds it in the disengaged position. I found a 12v source in the cab (under the dash). It will smooth out and the RPMs will increase slightly. The check engine light will come on. The CEL will clear the third start up after, if the toggle switch is put back in the off position. After flipping the switch to on, I usually just wait until the CEL comes on (it will when the tcc tries to engage at about 40 mph) and then flip the switch to "off". Once the code is set, the tcc will not again attempt to engage until the next start up (kind of a reset for the next start up).

I have put approximately 135-140,000 miles on the car using the switch. The car now has about 210,000 miles on it and it still runs great. I try to use the switch conservatively. During the winter, I never have the fishbite issue because the tranny doesn't get hot enough.

I haven't really noticed any drop in mileage with the tcc locked out. The increase in RPMs is only slight. It probably does use somewhat more gas when locked out.

The tcc does have 12v with the key in the on position. It does not lock in (no power to tcc) until the car reaches about 40 mph. When it gets up to speed, the power is shut off to the tcc and it engages, or locks in. It takes 12 volts to disengage the switch and hold it disengaged.

I found the wire by running a straight pin through each wire on the tcc (test each wire separately). Ran a wire into the cab to a 12v test bulb. Initially, the light was on. I started driving. When the tcc locked in at about 40 mph, the light went off and the fishbite started. If I applied a constant source of power to the wire, the tcc did not lock in and the fishbite never occurred. It turned out to be a fairly simple solution. From what I read, a correct fix would be to pull the transmission and replace the valve body. This would involve a complete rebuild, which would have run about $2,000 several years ago. The valve body seals get hot and fluid slips past causing the fishbite, or slip, when the tcc is engaged. The result is fishbite. Let me know if you need any further information on it.

If in fact the condition is the valve body and not an internal pressure loss the Sonnax valve body repair for the tcc valve will correct this. Other things can cause this, such as a skewed tps, bad o2 sensor, dirty injector/s, failing tcc and weak secondary spark. BTW disabling the tcc can, under severe driving condtions, cause the trans fluid to overheat as you are driving on the unlocked convertor which causes fluid temps to rise.

So, I do have the correct wiring harness? It is the round, six wire connector?

I have definitely found that the correct solution is a full rebuild, which would probably run at least $2,000 around my area. Such an expensive repair is not an option – the car is barely worth that much (according to KBB). But, since everything else in the car is perfect and the transmission appears to be undamaged, besides the TCC slipping; adding a TCC lockout switch is the perfect solution. Minimal cost, minimal labor, but maximum results (no fishbite).

Maxwedge – I have already determined that the TCC is the cause of my drivability issues. I am receiving DTC P1870 which directly mentions the TCC. The TPS, both O2 sensors, and plugs/wires have already been replaced.

The “fishbite” I experience occurs regardless of outdoor temperatures, but tends to worsen in extreme hot and extreme cold. The problem actually worsens (more noticeable, frequent) in the summer and winter months. If I installed the switch, chances are high that I would have to leave the TCC locked out for 100% of my driving time.

Is there any risk of damage by leaving the TCC locked out under all conditions?

I am thinking no – the recent cooling system work and transmission fluid changes should ensure the transmission never overheats. I am currently using Dexron VI, even though only Dexron III is necessary. From what I understand, the improvements in Dexron VI (full synthetic) should prevent the transmission from ever getting hot enough to cause damage – even under extreme driving conditions.

I have considered using Seafoam TransTune – would that make any difference? I have done 2 flushes/filter changes in the past 6 months. If I do add TransTune, I would be hesitant to do another flush/filter change because the Dexron VI that is currently being used was extremely expensive (~$6.50/quart).

Any suggestions? Thank you both for the help so far!

Well I'm no brainiac but if you said the correct solution was a full rebuild of the transmission, and you want to bypass the tcc in order to save money. Then save the money and do it.

what is the bad side to this. You ruin the transmission that already needs a complete rebuild anyway.

I really don't see the bad side to this.

But as I said I'm no braniac.

Well, the main issue is the risk. Due to age, and money, this car will likely never see a full transmission rebuild. I am a college student using the car as daily runner.

If I add the switch and the problem persists, or worsens, I can always just leave the switch off. My concern is any long-term risk of causing further damage to the transmission by leaving the TCC locked out permanently. I could just as easily do nothing and live with the fishbite, which is what I have been doing for almost 2 years now.

I do not want the transmission to fail prematurely due to this bypass – I am not in a position to purchase a new car. Opinions?

Driven moderately not towing or pulling hills you probably will not overheat the fluid, make sure what is in there now is not burnt or discolored. keep in mind you still have not found the root cause. The condition is exascerbated by the engine being " loaded" when in lock up.

I just went out and washed the wires a bit on the connector. The wire I called brown and black actually looks more like tan and black, now that I have it cleaned off. The wire left of it, and just a bit higher, is pink, or faded red and is a slightly heavier gauge. The connector is round and I counted 7 wires coming out of it.

You could easily test to determine if 12V will fix the problem if you run a straight pin through the tan/blk wire and clip an alligator connector on the pin. Run the other end to the battery and then drive it. It should remain locked out w/no fishbite as there would be a constant 12 v to the tcc. This might at least let you know if it will change the condition.

On mine, I had talked to a guy at a transmission shop. He told me I should just drive it until the transmission goes out all together. He said if they pulled it, they would want to do a complete rebuild anyway. I thought I might get 20 to 30,000 miles out of it before it failed completely. That was a long time ago.

The tcc won't lock in until you hit about 40 mph. My thought was, that if I were a person who only did in-town driving, the tcc would rarely or never lock-in anyway. This would be true in particular if driving across town from stop light to stop light and, say the speed limit was 30 or 35 mph. When it is locked in, pressing on the brake disengages the tcc instantly. For most of in-town driving, the tcc will never lock-in, unless it gets going fast enough.

Also, I did install a transmission cooler on the car. This only ran about $20 or $25. It attached to the radiator with some zip strips. Had to run lines to it to carry the fluid. I also use Lucas automatic transmission fluid additive in it and, Slick 50 auto transmission additive.

what kind of tranny is in car 4t60e or 4t65e

Different vehicle and a lot older, but I disconnected the lockup converter on my old 88 Century, and must have ran it 100 k like that and had no problems, and if I recall, no noticeable difference in mileage. The transmission was fine when my daughter's boyfriend drove a rod through the block at 330 k. It was easy back then, just pull the electrical plug from the housing...not like today's version. Just some info which may or may be helpful with your year.

That trans was the 3sp non o/d unit, the 4 spd o/d can be more problematic when running no TCC.

This is a 4T60-E( last year for the 60-E behind the 3800's )...

The usual cause for this is TCC valve bore wear.. But everyone needs to bear in mind that the 1997 has a different lock up strategy than say a 95.. The 97 can and will hit 3rd gear lockup early say 28-30 Mph...

He could even have a bad TPS causing some of his issues..

Also keep in mind that the 4T60-E will overheat if the TCC never applies... Regardless of weather or not you have cut the TCC wire, you risk frying the trans... I would be more willing to try a good sized tranny cooler if your problem only happens when the trans is hot..

You do need to check the TPS to make sure its operation is smooth with no jumps or sudden drops... Any issues with the TPS can cause a lot of driveability issues..

My Father and I took a look at the wiring over the weekend. We found the wiring harness, 7 wires, and determined that everything matched up correctly to the wiring diagram. The wires were out of order, but all the colors were correct. There was also small lettering on the black part of the connector (A, B, C) etc. we used to identify the wires. The letters are extremely small and difficult to read (C vs. G), but everything did appear to match up correctly.

Using a voltmeter, we determined that the PINK wire is the one that carries 12V to the transmission. This occurs when the key is in the “on” position – the 12V is hot constantly. Per the wiring diagram, this 12V is used for all of the control solenoids in the transmission. The TAN/BLK wire is ground. When the TCC is engaged, the TAN/BLK wire is grounded, completing the circuit and applying 12V from the PINK wire, thereby engaging the TCC. This behavior seems to hold true for all the solenoids.

We definitely found the problem. The TAN/BLK wire was being grounded (TCC Enabled) at ALL times, regardless of vehicle speed. The TCC was even engaged with just the key on (engine not started). This would explain my drivability problems – I was experiencing the fishbite on local roads (25-30 MPH) as well as on the highway.

So, we decided to cut the TAN/BLK wire and add a switch in the engine compartment. To prevent the TCC from enabling, you simply have to prevent the TAN/BLK wire from being grounded (cut the wire). The switch operates as such:

On – the TAN/BLK wire is connected back to the harness, grounding the TCC solenoid, enabling the TCC.

Off – the TAN/BLK wire is disconnected, resulting in an open circuit. The TCC solenoid is never grounded; therefore the TCC is never engaged.

The switch has been in the Off position for about a day now – no problems. The CEL is on, constantly, with code P0740 – Torque converter clutch circuit malfunction – which is to be expected. You can tell the car is trying to engage the TCC at any speed because the CEL returns immediately after clearing it.

I have had absolutely no fishbite. The TPS has already been replaced; it tested bad when I changed it. Should I really be concerned about adding a transmission cooler? I do absolutely no towing. The engine still has full synthetic Dexron VI – which I think should take care of any temperature issues.

Does anyone recommend adding anything like TransTune or Slick50? I am not going to drop the pan and do another flush anytime soon. It is odd that the PCM is enabling the TCC at all speeds – what could cause this behavior?

Thanks for all the suggestions!

It is odd that the PCM is enabling the TCC at all speeds – what could cause this behavior?

Usually, when the PCM is commanding ground at all times, the PCM is at fault! Do a search on eBay for a PCM. Usually you can find one for 80-bucks pre-programmed with the latest updates.

Interesting. Not sure about this. If the tcc was enabled at idle, in drive, or at all times, I believe it would kill the engine similar to pulling to a stop with a manual transmission, without pressing in on the clutch. Glad itis to be running smoother.

This actually all makes sense. I bought the car used when it had around 100,000 miles on it. If there were any previous drivability problems, they occurred and went away before I got the car.
If the TCC was being engaged at all speeds for an extended period of time (thousands of miles), then I would imagine that would cause excessive wear on the TCC bore from constant cycling on/off at lower speeds. Therefore, it is not outside the realm of possibility that this excessive cycling caused the TCC to begin slipping when it was engaged. I believe the TCC slipping is what caused the fishbite I was experiencing.

I have been driving the car since Sunday, absolutely no problems and no fishbite. It runs perfectly – I will be sure to post any gas mileage difference the next time I fill the tank. I hope this helps anyone in the future who experiences this same problem. Thanks to everyone for all the help!

My 4t25e tcc oscillates after warm up.
What if I use a cooler thermostat until I can put a new valve into the body?
Would the cool fluid aid in keeping the tcc engaged? Cool oil is thicker?
Add a trans cooler?
Summary:
Motor is perfect, and all tuned w/o any ck engine.
Tcc likes cool fluid (a viscosity issue)?
All shifts are perfect including oscillations.
What about additives? Lucas?
Dare i consider stp (one bottle)?
Will a new filter make for better flow?
I got this used and shifts are so good that i did not notice the tcc oscillation.
Fluid is red no burn and clear.
If I keep driving I fear the tcc clutch will wear.
Can i get help to temporarily cut the signal and keep the tcc clutch inactive?
Will anything else get the tcc out till I get a more permanant solution?
I guess it is possible to use a sonnax tcc valve seal kit, but is a difficult job for now.
Other ideas? I am still studying.
Much obliged.