Lock up clutch A442F (1 Viewer)

[NielsC]

Hi all.
I ran into a problem with my 1HDFT/A442F 80 series.
When coming home from a week out in the woods with cruiser I noticed the lockup clutch from the torque converter doesn’t seem to keep locked up that long as it did before in 4th gear. It feels like it releases sooner then it did before in relation to the throttle position, or feels like it starts slipping ik ne can’t handle the torque anymore when locked up.
I have lock up switch installed so I can manually activate the lockup clutch from in the cab, I never use it tough… but in 2nd and 3th I can go full throttle with the converter locked no problem, only in 4th it doesn’t seem to hold, even with only little throttle applied.
The oil does have a bit a burnt smell to it.
Throttle cable to gearbox is still good.
What should I do? Start with replacing the oil and maybe the lockup solenoid? Or does this sound like 100% fried lockup clutch?
Cheers

 

[NielsC]

Did a run on the highway today, sometimes the converter locks up in 4th gear and holds all the torque firmly full throttle, and sometimes it apears to not knowing what to do, lock up or not. Playing with the throttle can lock it up sometimes, or not.
Changed the oil today, it came out pretty dark brown instead of red.
Strange that it sometimes can hold the torque, sometimes not.

 

[A2ShedsJackson]

From the FSM:

Control of Lock-Up System
The TCM has programmed in its memory a lock-up clutch operation pattern for each driving
mode (Normal or Power). Based on this lock-up pattern, the TCM turns lock-up solenoid valve
on or off in accordance with the vehicle speed signals received from the vehicle speed sensor and
the throttle opening signals from the throttle position sensor.
Depending on whether lock-up solenoid valve is on or off, the lock-up relay valve performs
changeover of the fluid passages for the converter pressure acting on the torque converter clutch
to engage or disengage the lock-up clutch.

Mandatory Cancellation of Lock-Up System:
If any of the following conditions exist, the TCM turns off lock-up solenoid valve to disengage
the lock-up clutch.
(1) The brake light switch comes on (during braking).
(2) The IDL points of the throttle position sensor close (throttle valve fully closed.).
(3) The vehicle speed drops 4 km/h (2mph) or more below the set speed while the cruise control
system is operating.
(4) The coolant temperature falls below 70C (158F).
The purpose of (1) and (2) above is to prevent the engine from stalling if the rear wheels lock up.
The purpose of (3) is to cause the torque converter clutch to operate to obtain torque multiplica-
tion. The purpose of (4) is both to improve general driveability, and to speed up engine warm -up.
Also, while the lock-up system is in operation, the TCM will temporarily turn it off during up-
shift or down-shift in order to decrease shifting shock.

No lock-up in 3rd or O/D

Possible cause:
Electronic control faulty
Valve body faulty
Solenoid valve faulty
Transmission faulty