I haven't driven my chevelle in sometime. . .well since the north east chevelle show in late june. Then I've proceeded to put a 4 core radiator in it and I've just been fooling around and in no hurry to put it in. I finally got it in and put coolant in and it's all ready, but when I got home today it left me a present. A big puddle of transmission fluid under her. I guess she's tired of sitting around in the garage. How could this have happened all of a sudden fluid just leaks out even though it hasn't ran in a couple of weeks?

Radiator return lines?

It could mean that you converter /pump seal is bad. My buddy had the same problem on his hotrod oickup. If it sat for too long it left a lake of tranny fluid. They don't like to sit :)

I had a T 350 that would do that.

Leave the car parked for a couple of weeks and it would have a big puddle of tranny fluid underneath, drive it around the block and the leak would stop.

Sounds like a dog I had. If I didn't let it out to play every so often, it would pee on my floor.

The TH400 in my 70 does that every now and again. If I drive it, then let it sit for a week, it will pee tranny fluid on the floor of the garage.

This is usually caused by the torque convertor draining into the oil pan and overfilling to the point it will run out around the dipstick tube O ring. The O ring isn't designed to keep oil in at that level.

This is usually caused by the torque convertor draining into the oil pan and overfilling to the point it will run out around the dipstick tube O ring. The O ring isn't designed to keep oil in at that level.


My thoughts exactly.

Sometime in the late 70's or early 80's Gm changed the design of the dipstick/fill tube. The changes were made to both 350 and 400 transmissions. This may have been done to stop just this type of leak. Instead of an O ring they used a tapered rubber sleeve about an inch long. The dipstick/fill tube was made smaller at the bottom end to fit inside the sleeve. The transmission case was not changed so this later model set up will fit the early cars and still look stock from the top. If changing to this type make sure the tube is the same length as your old one or get the tube and dipstick as a set from the donor vehicle.

If the O ring isn't designed to hold back the fluid once the car has been sitting for a while, could it also mean that there's too much fluid to begin with?

OR, you filled up your radiator, which drained into the trans due to the internal radiator tranny cooling lines leaking, and tranny fluid went out the top vent tube....

If that's the case, don't start the car until you flush out the antifreeze in the tranny & fix that leak.

typical hydramatic drainback from sitting,from the reasons stated above.

Thats what pallet sized cardboard slip sheets are for :D

Don't overthink it.Top it off and move on :)

First, check your fluid level (check for traces of antifreeze while your at it).
Next SNUG not tighten pan bolts. Wipe everything of, carb spray and wipe would be better,
Go about your business, peek under there now and then for leaks. Serves you right for not taking the Chevelle out more often. SHAME ON YOU!!!!!

Time can cause a gasket to get saturated in tranny fluid, especially the cork gaskets. If your trans was 1/2-1 quart low, it would have still functioned normal and while driven regularly, the fluid stayed below the gasket line and you never saw any puddles. But when you parked it, all the fluid drains out of drums, valvebody, etc...and fills the the pan above the gasket line. Same thing as the dipstick deal.

At one time, my car would leave a puddle only when I parked in the driveway. Changed pan gasket twice, still leaked, but only in the driveway, parked overnight. It was the tail housing gasket, bleed down and driveway angle was the magic combo.