Sounds like that converter has failed, did you follow this test.
Stall Speed Test
NOTICE: Carry out the Line Pressure Test prior to the Stall Speed Test. If line pressure is low, do not carry out the stall test or additional transmission damage will occur. Do not maintain Wide Open Throttle (WOT) in any gear range for more than 5 seconds.
NOTE: After testing each of the ranges, move the selector lever into the NEUTRAL position and run the engine at 1,000 rpm for about 15 seconds to allow the torque converter to cool off before continuing onto the next range.
NOTE: If the engine speed exceeds maximum specified rpm, release the accelerator pedal immediately.
NOTE: Only perform the stall speed test with the engine and transmission at normal operating temperatures.
The Stall Speed Test checks the operation of the following items:
Torque converter reactor One-Way Clutch (OWC)
Forward clutch
Low OWC
Overdrive OWC
Engine driveability concerns
Connect a scan tool.
Press the accelerator pedal to WOT in each range. Record the rpm reached in each range. Stall speeds should be in the appropriate range.
Stall Speed
Engine Drive Reverse Diesel 1,600-1,750 rpm 1,800-2,000 rpm Gas 2,100-2,300 rpm 1,900-2,200 rpm