I have a 1966 mustang with a C4 automatic with atransmission leak that I cannot figure out.
I let the car warm up, check the fluid level and correct ifnecessary. I then check under the car while idling in park and drive for leaks.All is dry. I will then take the car for a drive and bring it back into thegarage. I then check for leaks and everything is dry. The next morning there isa puddle of transmission fluid under the car.
I have tried about every pan gasket and gasket sealer knownto modern man. My procedure is to clean the mating surfaces and dry them. Ialso make sure the pan flange is flat. I then install the pan and tighten thebolts to the recommended torque.
When I inspect the outside of the transmission after itleaks it is dry around the case fill dipstick, transmission modulator, shiftershaft and overflow tube.
Is there somewhere other than the pan it might be leakingfrom?
When the car sits, the torque converter drains back into the pan, raising the oil level.
Let the car sit overnight (or however long it takes for the leak to show) and pull the dip-stick *before* you start the engine.
It should read high up the stick.
Now get under and check *really carefully* around these areas....
1. At the base of the fill tube/dip stick tube.
2. Linkage seal area
3. Front servo cover.
My money is on the fill tube O-Ring.
Here's what happens... when the car sits and the converter drains back as mentioned above...
... the fluid level gets above the fill tube O-Ring, and leaks past the O-Ring.
That leak then runs down and around the pan gasket, making it *look like* the pan gasket is leaking.
When the engine is running, the "Full" level on the stick is approx at the level of the pan gasket,
which is *below* the level of the dip-stick tube O-Ring.
So it never leaks while it's running.
When you inspect for the leak after the car sits... look very closely at the case area around and below the fill tube.
Use a good bright light and a clean white rag to wipe the area at the base of the fill tube.
I bet you find your leak.
If not that... then next likely place is the linkage seals.
These can leak in the same manner as the dip stick tube.
As mentioned above, it could also be the front pump gasket or front seal, tho those "should" leak all the time.