Transmission Leak Question

[Cupid]

I have a C-6 on my 70 Grande'. It must be a tranny swap by the guy who had it before me. Anyway, I've had it for about 6 months and the tranny has never leaked. Well, that is until I noticed it being about quart low on the dipstick. I filled it and checked it properly(in park, after a drive around the block to heat it up). It has leaked small amounts of fluid(about the size of a grapefruit) everytime I drove and parked it for about a week. Here's the weird thing. There seems to be a drain hose connecting to the top(aft) part of the tranny. It seems to be where the fluid is coming from. From the looks of it, it seems to be some sort of overfill tube to let out excess fluid. Is this correct? How hot does my tranny have to be before checking the fluid level? I fear that I may be overfilling it, or worse....something else is wrong. BTW, I checked the dipstick partnumber via the Restoration guide and it's correct. Also, it doesn't leak when it is about a quart low. No slipping, etc...

 

[1969mach1351]

I think you need to drive it for at least 15 min to get the tranny up to temp. My FMX tranny will barely go into gear if it is a quart low. From what I have read you are supposed to check the fluid while the engine is running and go through all the gear positions right before you check it. I think you are right about it having an overflow tube.