richardkf wrote:
Torque Converters only lock up in the highest gear.
This is from the service manual
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and turbine
are rotating at about the same speed and the
stator is freewheeling, providing no torque multiplication.
By applying the turbine’s piston and friction material
to the front cover, a total converter engagement
can be obtained. The result of this engagement is a
direct 1:1 mechanical link between the engine and the
transmission.
The clutch can be engaged in second, third, fourth,
and fifth gear ranges depending on overdrive control
switch position. If the overdrive control switch is in the
normal ON position, the clutch will engage after the
shift to fourth gear, and above approximately 72 km/h
(45 mph). If the control switch is in the OFF position,
the clutch will engage after the shift to third gear, at approximately 56 km/h (35 mph) at light throttle.