Okay, I had a used tranny installed to replace a cooked one. Seemed fine at first, but was just city driving. Seem that when I go over 40 and let off the gas to coast, the tranny will go into neutral with a grinding sound. If i give gas, it reengages and works just fine till i coast again. It shifts fine through all the gears, no slipping being noticed. I've put about 200 miles since being replaced and the fluid is full and red. I'm thinking the input speed sensor might be bad, any ideas?