4L80E HEAVY DUTY USE TRUCKS, SHIFTS 1-2-3-1 WE HAVE FOUND THAT SIGNAL B OIL OVERCOMES SIGNAL A OIL. WE'VE ENLARGED SIGNAL A HOLE TO .044 THAT WAS A TEMPORARY REPAIR. WE'VE REDUCED SIGNAL B HOLE TO .010 THAT WAS A TEMPORARY REPAIR. WE'VE CLOSED SIGNAL B HOLE CO... Login to read more.