You sometimes get a drip but for it to be gushing out the seal must be completely shot or missing. When you take the box out again check the input shaft bearing for wear, I had a similar problem with an overdrive box and found the seal and bearing were shot - it must have been stored upright on the bell housing end for a long time in poor conditions so water had run through it and settled at the input shaft. Hopefully that won't be your issue.