Just finished my swap (LQ4/4L60E). Reverse worked, dropped it off for exhaust now not working? Forward gears work fine. RPM drop slightly when I shift to reverse, linkage is good. Fluid looks good. Wiring appears to be intact. I didn't have the car running long enough to know the real health of the transmission, just that all gears worked without issue. Is my transmission toast or could it be a an electronic issue?