Lockup Torque converter

[nicv21]

Hi all!

My 2001 Pathfinder has developed a quirk in the lockup torque converter. After starting off from cold, it drives and shifts great. In about 150 yards when I come to a stop the Transmission does not disengage and tries to stall the engine. I pop it into neutral and then back into drive and it goes, but I can feel there's a problem. After a minute after I see temp on the gauge it's all good.

It doesn't always do this, but I am sure it's going to get worse before it gets better. I think that it's the valve in the transmission, and I can drop the pan etc. and replace it, BUT is there some other control module that triggers this valve?

I'm assuming that the vale when energized ports fluid from the pump to the Torque Converter through this valve in the open status. When it closes I assume that the torque converter clutch is disengaged. Or am I bass ackward?

[VStar650CL]

Virtually all converter lockups are direct acting -- i.e., there are no springs involved and hydraulic pressure locks the clutch, cutting the pressure lets it freewheel. BUT, the way the solenoids are arranged electrically and the valves are arranged hydraulically is potpourri. There are a lot of Nissans which use "dead man switch" arrangements where the lockup defaults to locked and the TCM needs to drive the solenoid to unlock it. Glancing through the hydraulic diagrams, it looks like your Pathy is one of those. If the solenoid resistance was off electrically the TCM would be throwing a code, so my first guess is that your intuition is right, it's a sticky valve.

[nicv21]

VStar650CL, Thanks for the response. I am very familiar with lockup torque converters, first one I worked on was on a Jaguar 60's 3.8 coupe with a Borg warner DG transmission. It energized through the input shaft, and it was totally mechanical in operation. So, no pressure, no lockup, BUT it did have a clutch pack and springs to release. I am going to check the codes as my Pathy is in a constant state of illumination, and it's always something frivolous like non-OEM O2 sensor. It runs great with over 225,000 miles, passes emissions. I did have the transmission flushed about 2 years ago, so maybe it's time to do it again. Or I might just drop the pan and see if there's a reason the valve might be sticky.

[VStar650CL]

Nissans work the same way as that Jag mechanically, but most of them vent pressure on the back side of the hydraulic circuit to relieve the clutch rather than cutting it off on the front end. Hence, the "dead man" behavior in many of them.

At 225K you might just have a worn out VB.