I have a 94 formula that i got and put in an rebuilt corvette spec LT-1 and rebuilt the 4L60E. After all the rebuilt and install was done we drove the car and for the first day so far so good. The second day we took it out for a 50 mile drive and when we were almost back home when the car all of a sudden started to downshift and eventually stayed in first gear and limped home. The car goes into gear and after a couple of minutes when it gets warm the same deal. Also when you start the car there is a weird humming sound. We opened it up found the filter cloged and cleaned all the cooler lines and transmission guy changed the 4th gear clutches that got burned (new rebuilt kit!!!) He also checked the valve body and put it back together.
Same thing happened again within the same timeframes. The transmission guy says that it may be the converter, others say it may be the pump, both were replaced with rebuilt units. Any ideas I don't want to get any further in my pockets before I have a slight idea. Any input greatly appreciated and very valuable