904 kicking out of gear

Understood. I'll try to explain some of it. The throttle pressure linkage (that's what everybody calls the kickdown linkage but the correct name is throttle pressure linkage) goes farther back the more you push the accelerator down. When the engine is at idle the throttle pressure linkage is all the way forward. The shifter linkage is in park when it's all the way rearward. As you shift down through the gears towards low gear the shifter linkage on the trans comes forward. If the throttle pressure linkage is catching on the shifter linkage it will naturally push the shifter linkage back into neutral as you press down on the gas. Hope that makes sense.