Repair-It

P0741 = Failed Turbine Shaft Seals

A Viscous Coupler (VC) is a sealed unit. A TCC vc has clutch plates and a Silicone fluid in it. When the plates start rotating at two different speeds, the shear effect of the tabs or perforations on the fluid will cause it to heat up and solidify (Silicone when heated will turn into a near solid; the viscosity of dilatant fluids rapidly increases with shear). The fluid in this state will essentially glue the plates together and transmit power from one set of plates to the other. This increases the pressure inside of the sealed drum. If the pressure increases to much it will crack the VC drum.

Now you have bad seals and a bad VC.
This is very common and that is the reason GM states that the Torque Converter must be replaced.

I have seen several tech try to short cut this and not replace the TC. I don't think this has ever worked more that 5 times that I have seen in the last 5 years. They always come back with in a month and the tech has to do it over again.

I will post some pictures of GM's VC used in the TC

ENERAL DESCRIPTION

http://i224.photobucket.com/albums/dd25 ... s/TC/1.jpg

As shown in figure 1, the 12.2 inch converter does not include a torque converter clutch. This type of converter is commonly referred to as an "open" converter. The 245 mm and 298 mm are sometimes referred to as a "closed" converter. The terms closed and open refers to the fluid flow through the converter with and without the use of a torque converter clutch (TCC).

Note: The torque converter operation in this book refers to the 245 mm and the 298 mm with the use of a TCC. However, the differences with the 12.2 inch (310 mm) "open" converter are pointed out as appropriate.

TORQUE CONVERTER ELEMENTS

The torque converter assembly serves three primary functions. First, the torque converter is a fluid coupling that smoothly transmits engine torque to the transmission gear-train. This fluid coupling also allows the vehicle to stop without stalling the engine. Secondly, it multiplies torque. from the engine to the transmission for additional vehicle performance. Finally, the torque converter assembly provides a mechanical (or direct drive) link from the engine to the transmission with the use of a torque converter clutch (TCC).

A 245 mm or 298 mm "closed" converter has four elements (Fig. 2). This design contains a converter pump assembly (driving member - I), a turbine assembly (driven or output member - F), a clutch pressure plate assembly (C) splined to the turbine to provide direct drive, and a stator assembly (reaction member - G). The converter cover (A) is welded to the pump to seal all four members in a fluid filled housing. The 12.2 inch (310 mm) "open" converter has three elements. This design contains a pump (I), turbine (F), and stator (G), but does not have a clutch pressure plate assembly.

http://i224.photobucket.com/albums/dd25 ... s/TC/2.jpg
http://i224.photobucket.com/albums/dd25 ... s/TC/3.jpg

The converter cover (A) is bolted to the engine flex -plate which is bolted directly to the engine crankshaft. Therefore, the converter pump is mechanically connected to the engine and turns at engine speed whenever the engine is operating.

The converter pump (I) acts as a centrifugal pump, picking up fluid at its center and discharging this fluid at its rim between the blades (Fig. 3). It is the force of this fluid from the pump hitting the turbine blades that causes the turbine to rotate. When the engine is idling in gear, the converter pump is not spinning fast and the force of the fluid leaving the pump is not great enough to turn the turbine and move the vehicle. As engine speed increases, fluid force increases and more engine power is transmitted to the gear train. Turbine speed does not reach engine speed until the torque converter clutch (pressure plate) is applied. Thus, there is a small amount of slippage in this fluid coupling between the converter pump and turbine.

http://i224.photobucket.com/albums/dd25 ... s/TC/4.jpg

The pressure plate (C) is splined to the turbine hub. It applies against the converter cover to provide a mechanical (direct drive) coupling of the engine to the transmission. This mechanical coupling provides a more efficient transfer of engine torque to the drive wheels by eliminating the small amount of slippage that occurs in a fluid coupling. Thus, with the pressure plate (TCC) applied, the turbine assembly turns at engine speed and torque is no longer being multiplied.

To aid in torsional shock during converter clutch apply, a damper assembly (D) is used with the converter clutch pressure plate (C). The spring loaded damper assembly is splined to the converter turbine assembly (F). The converter clutch pressure plate is attached to the pivoting mechanism of the damper assembly. This pivoting action allows the pressure plate to rotate independent of the damper assembly, up to approximately 45 degrees. The rate of independent rotation is controlled by the pivoting mechanism acting on the spring in the damper assembly. The cushioning effect of the damper assembly springs aid in reducing converter clutch apply feel and irregular torque pulses from the engine or road.

The stator (G) is located between the converter pump and turbine and is mounted on a one way roller clutch. The purpose of the stator is to redirect the flow of fluid returning from the turbine to assist the engine in turning the converter pump. This redirection increases the force of the fluid driving the turbine and, as a result, multiplies torque from the engine (Fig. 4). If the fluid from the turbine was not redirected at low vehicle speeds it would impede the rotation of the converter pump.

http://i224.photobucket.com/albums/dd25 ... s/TC/5.jpg

At low vehicle speeds, when greater torque is needed, fluid from the turbine hits the front side of the stator blades (converter multiplying torque). Because the roller clutch holds the stator from moving in that direction, fluid is redirected from the turbine to assist the engine in turning the converter pump. Fluid from the converter pump then has more force to turn the turbine assembly and multiply engine torque.

As vehicle speed increases, centrifugal force changes the direction of fluid from the turbine. The direction of this fluid is such that it hits the back side of the stator blades (converter at coupling speed). This causes the roller clutch to overrun and allows the stator to rotate freely. Fluid is no longer redirected and engine torque is not being multiplied


TORQUE CONVERTER CLUTCH

As mentioned previously, the torque converter is not 100% efficient (up to a 10% loss) at coupling speed without the TCC applied.

The energy from the engine is wasted by the torque converter in the form of heat. This heat created by the slippage between the converter pump and turbine is the largest source of heat for transmission fluid. Thus, if this energy can be captured, we could increase the fuel economy of the vehicle and also reduce transmission fluid temperature. The torque converter clutch performs this task. The converter clutch functions similar to a standard transmission clutch by mechanically connecting the engine to the transmission. This makes the torque converter 100% efficient, thus increasing fuel economy and reducing transmission fluid temperature. The actual speed at which the TCC applies varies between vehicle applications.

There are three types of pressure plates in the present Hydra-matic converter assemblies. Two of these have spring type torsional dampening and the third has a viscous torsional dampening.

With the spring type damper, (Fig. 2), as the TCC applies, the springs in the damper assembly compress and allow the pressure plate to pivot. The pressure plate is allowed to pivot independently of the turbine to approximately 45 degrees. The spring cushioning effect aids in reducing the converter clutch apply feel.

A poppet style pressure plate is used with diesel engine applications (Fig. 5). With this type of pressure plate the

spring damper uses additional fluid control valves. These valves equalize fluid pressures on both sides of the pressure plate during TCC disengagement. This allows the pressure plate to release quicker and reduce torsional vibrations during deceleration on diesel applications.

http://i224.photobucket.com/albums/dd25 ... s/TC/6.jpg

VISCOUS CONVERTER CLUTCH

The third type of pressure plate is the viscous converter clutch (Fig. 6). The viscous clutch is only used on some HYDRA-MATIC 4T60 and 4T80 transaxles to provide a smoother apply feel. The viscous converter clutch performs the same functions as the conventional converter clutch explained earlier. The primary difference between the converter clutch and the viscous converter clutch is the method of dampening the apply feel. In the viscous clutch the spring damper is replaced by using viscous (thick) silicone fluid sealed between the body and cover of the clutch assembly. This fluid provides a smooth apply of the clutch assembly when it engages with the converter cover.

http://i224.photobucket.com/albums/dd25 ... s/TC/8.jpg

When the viscous clutch is applied (Fig. 7) the silicone fluid grips the intertwined ridges of the body and rotor of the viscous clutch. With the rotor splined to the turbine hub this forces the turbine to rotate at nearly the same speed as the converter cover. With this viscous apply there is still a minimal amount of slippage between the rotor and body.

http://i224.photobucket.com/albums/dd25 ... s/TC/7.jpg

I work on nuclear subs

The 4T80E transmission is not that complicated - it's merely impossible to get far into while still in the car, and removal is no picnic. The solenoid can be replaced with the transmission in the car, but the job is sort of like remote control surgery.

(Diesel boats, fast attacks, COB on two SSBN's. QMCM(SS)(DV))

You got that right. I just did the solenoid replacement with the powertrain in the car. But, in all honestly, most of the job was removing everything else in the way. The motor mount bracket was a real b*tch. After the side cover was opened, it took about an hour to r/r the solenoid and clip. I used a mirror and some aluminum welding wire. I slid the wire thru the rounded end of the clip and bent it over to avoid dropping it, and used my forefinger and thumb to remove the clip. The solenoid was easy, slip the old one out, wet the o rings with some new trans fluid on the new solenoid and slide it in. I fabricated a holder for the clip to align it with the slot, and pushed it in. But it took a few tries.Lucky me, I have another one to do on my son's Deville yet.

former STS2(SS)
Submariner409
09-13-11, 10:38 PM
Ping jockey..............Forward puke - finest kind............Had you figured for a nuke ET. Sorry. At least you're good at working on incredibly tiny servos with broken belts in impossibly cramped spaces with improper tools. Sort of like the FT's working on the Torpedo Fire Control console..................

"Sonar, Conn. We're preparing to hover................"

Good job. Someone else did roughly the same fix about 5 months ago........... it's in here somewhere.................
bigtone
09-14-11, 07:02 PM
Where I work we call people Navy Nuke ET as an insult. I thought 'ping jockey' was reserved for the surface guys. Usually we got called 'sonar girls'.......

Here's a TCC failure, with catastrophic consequences to the transaxle:
http://www.cadillacforums.com/forums/no ... lutch.html

Note that not all P0741 failures will lead to a catastrophic transmission failure. If you are having other transmission mechanical issues besides P0741, or if you are having a whining noise of some sort, my thread is worthy to look at.

Also if you are having P0741 + P1860 then it's a broken TCC PWM solenoid, not TCC itself.

kevm14 wrote:The Lucerne was actually on the G-platform.

https://www.caranddriver.com/reviews/20 ... -road-test

From a standing start, you get an initial jump off the torque converter up to 7 or so mph, followed by a sag as you wait for the twister V-8 to take over, which it does at about 28 mph; 60 mph comes up at just a tick under seven seconds (6.9), followed by the quarter-mile mark in 15.3 at 94 mph.

Yay I win. And yeah drivability seems a little lame as I also predicted. But not bad for $1,000. Should feel a little stronger than the 94 9C1 on a roll, but without the launch torque.

Although a V-8 driving the front wheels is out of step with today's trend back to rear drive, the Lucerne makes it seem as right and righteous as God's plan. What torque steer? More to the point, what torque? For the record, the 4.6-liter Northstar is a twister, not a torquer, delivering 275 horsepower at 5600 rpm, with another 1000 rpm available before the redline, but a torque output of only 290 pound-feet at 4400 rpm. Compared with, say, the 390 pound-feet at 4000 rpm of Chrysler's Hemi, the Lucerne's V-8 is only mildly energetic.

We'd call the Lucerne agile but hardly athletic, possessing neither the muscular stride of the Hemi nor the flaccid indifference to motion of the Ford Five Hundred. The emphasis here is smooth quietude--quiet smoothitude?--with only a smooth-jazz moan from the Northstar at full stomp.

I love the Red & Black interior and seating that was available in the C5 Z06. For me, the perfect C5 Z06 would be a 2003 in Electron Blue with this Red & Black interior. Even this 385 HP 2001 Z06 was & still is an amazing performer. But the improvements and power gains for 2002 really made a difference. I've seen completely bone stock 02-04 C5 Z06's on their stock Goodyear Eagle F1 Supercar tires running between 12.2-12.4 @ 116-117 mph! Absolutely incredible performance. What a car!

GM stopped using the VC in 4T80E in 2005

Torque Slip Speed Limit
lb ft RPM
0 48
47 80
94 200
142 252
189 271
236 280

Circuit Description
The PCM controls the torque converter clutch (TCC) solenoid valve pulse width modulation (PWM). The solenoid controls the hydraulic fluid for TCC apply and release. When the TCC is applied, the engine is coupled directly to the transmission through the TCC. The TCC slip speed should be near 0.

If the PCM detects high torque converter slip when the TCC is commanded ON, then DTC P0741 sets. DTC P0741 is a type B DTC.

Conditions for Running the DTC
• No MAF DTCs P0101, P0102, P0103.

• No MAP DTCs P0106, P0107 or P0108.

• No TP DTCs P0121, P0122 or P0123.

• No VSS DTCs P0502 or P0503.

• No AT ISS DTCs P0716 or P0717.

• No TCC stuck ON DTC P0742.

• No IMS DTCs P1820, P1822, P1823 or P1825.

• No TCC PWM solenoid valve DTC P1860.

• The engine run time is greater than 5 seconds.

• The time since the gear select lever change is greater than 6 seconds.

• The IMS indicates D2, D3 or D4.

• The transmission gear ratio indicates 2nd, 3rd or 4th gear.

• The transmission fluid temperature is 20-133°C (68-271°F).

• The TP angle is 10-50 percent.

• The engine torque is 43-215 N·m (32-159 lb ft).

• The TCC solenoid valve is commanded ON.