4T60: 5-speed tranny?

[TeeJay3800]

Has anyone noticed that their 4T60 tranny seems to shift 5 times? I know that its a 4 speed automatic, but the RPMs drop 5 times and I hear/feel what I take to be five shifts taking place. I think I read somewhere that around 32-37 MPH some sort of clutch type thing engages to make a direct connection with the wheels or something. That may explain why it seems to shift 5 times. Does anyone know what I am talking about or can tell me what this is all about

[RebelGT]

You are feeling the TCC (torque convertor clutch) engaging and disengaging.

[TeeJay3800]

Ahh I see. So what is the purpose of the TCC? What does it accomplish?

[JayBear]

Ahh I see. So what is the purpose of the TCC? What does it accomplish?

Basically, its just a clutch in the torque converter which improves fuel milage. Since it is impossible to achive 100% lockup in standard converters they now put clutches in there. Its controled by the ECM, and once it is locked up it is soposed to achive nearly 100% effiency, so you will not lose any power between the engine and the trans.

[TeeJay3800]

It makes sense that the clutch is controlled by the ECM cuz I notice it engages later when the A/C compressor is running. The near 100% effiency does too becuase throttle response seems a lot better with the TCC engaged. Now the question is, about how much effiency of power is transmitted without the clutch engaged?

[robby1870]

It makes sense that the clutch is controlled by the ECM cuz I notice it engages later when the A/C compressor is running. The near 100% effiency does too becuase throttle response seems a lot better with the TCC engaged. Now the question is, about how much effiency of power is transmitted without the clutch engaged?

I have heard like 25-30% power loss from an auto w/o the TC locked up. TC lockup is based on the VSS, A/C and engine load, and prolly some others too