Leak at speedo cable.

Unfortunately that's a leak prone area on torqueflite's. There are 2 seals in the speedo housing. The main outer O-ring and the speedo pinion gear seal. The outer seal doesn't usually cause a problem but it can. It's usually the inner speedo gear seal that leaks and I've had problems with numerous ones I couldn't stop from leaking until I found an updated seal that does a great job of sealing it up. It's a real easy fix. All you have to do is unscrew the speedo cable and take out the speedo pinion adapter (one bolt). Remove the speedo pinion gear and replace the internal seal and re-assemble it making sure to get the speedo adapter clocked right. While your there you might as well also replace the outer seal cause sometimes even if they aren't leaking once you take them apart it disturbs them and they start leaking. Use a little light grease on the seals when re-assembling them. If you jack the car up from the rear only you won't loose much fluid at all cause it'll all run into the main case. It generally takes longer to jack the car up and let it back down than replacing the seal.

I buy the seals from www.bulkpart.com Unfortunately they don't have the updated speedo gear seal listed. You have to call them to order it. Call Mike and tell him what your problem is and he'll know what seal it takes to upgrade. If you have any trouble getting one let me know. I can also scan a picture of the speedo housing parts showing the seals and post it if you need it.