What controls the lockup on a torque converter?

 

1995 4EAT

 

I am getting what appears to be a premature lock up of the converter when it shifts from 2nd - 3rd. It locks up for a moment and then unlocks in 3rd. I get the corresponding reduction in RPMs and then they climb again. Then it again locks up at the right time, after the shift to 4th.

 

 

Can you disconnect the lock up some way, so I can test? Is it part of all that stuff attactched to the passenger side shock tower?

 

Thanks

The TCU controls the TCC Lockup solenoid directly. There is no outside source.

 

The fuse on the strut tower is for the AWD transfer clutch duty solenoid. Has nothing to do with the TCC.

 

There can be several things wrong here, incorrect vehicle speed input to the TCU causing it to lockup the TCC early, Throttle position input, or more likely a bad wire connection between the trans harness connector and TCU, or a damaged wire inside the trans or poor ground connection, or a failing solenoid.

Input power from the TCU to the lockup solenoid appears to be a Red/Yellow wire on pin 6 of the trans harness connector.

The lockup solenoid is grounded to the transmission case.

 

Is the transmission pan dented in any way? Look for marks that would indicate the ears of a jack head have been in contact with the pan. Any amount of weight placed on the transmission pan can cause damage to wires or solenoids inside the transmission.

No damage to the pan....I will look for damaged or worn connections.

 

Thanks for pointing me in the right direction!