How do you test the stall speed of the converter?

 

Left foot VERY firmly on the brake. Right foot all the way to the floor, FOR NO MORE THAN 5 SECONDS!!!!!!!!!!!!!!!!!! Then let it run in neutral to cool the converter. The converter will get VERY, VERY hot doing this.

 

In 2 seconds the tire would be melted

 

Put it in 4x4 then you have four brakes to hold the torque. Don't use 4x4L.

If that doesn't work then you can't test the stall speed.