Torque Converter Lock-up Clutch

[wwest]

The more I learn about this the more scared of the future I get.

Just now had a good conversation with a third party automatic transmission technician.

He said that earlier lock-up clutches did tend to fail prematurely (the one in my 2001 RX300??) due to the inability of the controlling ECU to have close enough control to prevent clutch slippage on engagement and in some cases even while engaged. According to him the industry has recently changed the clutch design to a carbon fiber frictional surface. Apparently carbon fiber is a lot more tolerant of the high level of slippage incurred in ECU controlled transmissions.

He also stated that if the lockup clutch is engaged it will be disengaged for each shifting sequence and then re-engaged once the shift sequence is complete.

Don't know if any of this applies to the hesitation issue but I have never found more information to be detrimental.

That new BMW X3 w/manual transmission is looking more and more attractive every day.

[ColinBarber]

Was does he mean by early ones? Toyota have used them for over 20 years.

However this ties in with what SKperformance found with his transmission as the friction material was in the fluid and why he recommends an external filter.

[wwest]

Historical data...

Yes, lockup clutches have been in use for many years.

But only with the advent of FULL electronic control of the shifting has the lockup clutch begun to be used in other than O/D mode.

As I understand it, with ECU control the lockup clutch is now engaged anytime the vehicle is in "cruise", no substantial level of engine torque, mode. Disengaged for acceleration, any shifting sequence and/or when coming to a stop wherein the engine would stall if the "solid" coupling were maintained.

[ColinBarber]

As I understand it, with ECU  control the lockup clutch is now engaged anytime the vehicle is in "cruise", no substantial level of engine torque, mode. Disengaged for acceleration, any shifting sequence and/or when coming to a stop wherein the engine would stall if the "solid" coupling were maintained.

←

Lock up is being used more and more. For example the GS400 used to use lock up in 4th and 5th gears once a certain speed had been reached. In 2001 with the GS430 lock up now occurs in 3rd, 4th and 5th gears.