Leaking transmission fluid from overflow

not told at all which end leaks (the exact spot matters)
I bet there is lots more wrong !
when did car last run good, or not leak ATF
last week,, last year, last decade? what?clues help.

history matters on all and service done. for 39 years
last owner left the pan loose and 2 bolts left and 5 turns loose, we cant see under any car.
front seal blown on or behind TC
rear seal; blown
pan gasket a wreck
pan hit rocks and cut and leaks
side shifter rod seal blown
or sensors on it leak (VSS)
governor cap seals blown./
more, sure.

2004 doesn't have a modulator valve . An if it did it would affect all gear operation , Shift hard , but would still go into gear. You have an internal transmission problem !
No Reverse, Slips in Reverse
Checks
Causes
Reverse Clutch
No apply or slipping
Piston and Seal Assembly (457)
Binding, cracked, or leaking
Inner Seal (456)
Plugged orifice
Clutch Plates (460-463)
Worn friction or broken splines
Snap Ring (459, 464)
Out of position
Housing (454)
Cracked, plugged feed holes, or broken tangs
Housing Retainer and Ball Assembly
Missing or out of position
Springs (458)
Binding
Reverse Clutch Fluid Routing
Fluid leak or restriction
Driven Sprocket Support (95)
?€¢
Leaking seal rings

?€¢
Porosity, damage, misalignment

Channel Plate and Gasket, and Valve Body, Gaskets, and Channel Plate
Porosity, fluid leak across the channels, misalignment, damage, or fluid restriction
Low and Reverse Band and Servo
No apply or slipping
Servo Piston (69)
Broken or binding
Servo Piston Seals (71, 72)
Leaking
Servo Pin (67) and Springs (66, 68)
Binding
Servo Cover (73)
Broken, loose, or leaking
Low and Reverse Band (111)
Broken, worn, or out of position
Anchor Pin (64)
Broken
Fluid Feed Tubes (83)
?€¢
Broken, bent, or plugged

?€¢
Missing or leaking seal rings

Transmission Case (1)
Porosity, fluid leak, or restriction
Shift Linkage
Disconnected or misaligned
Manual Valve (800) and Link (802)
Disconnected or misaligned
#1 Checkball
Missing, no low band fluid
Fluid Level
Low
Fluid Pressure
Low
Refer to High or Low Line Pressure .
suggest you take to an ASE certified transmission repair facility !

There are several thing's that can cause a no reverse !
No Reverse, Slips in Reverse
Checks
Causes
Reverse Clutch
No apply or slipping
Piston and Seal Assembly (457)
Binding, cracked, or leaking
Inner Seal (456)
Plugged orifice
Clutch Plates (460-463)
Worn friction or broken splines
Snap Ring (459, 464)
Out of position
Housing (454)
Cracked, plugged feed holes, or broken tangs
Housing Retainer and Ball Assembly
Missing or out of position
Springs (458)
Binding
Reverse Clutch Fluid Routing
Fluid leak or restriction
Driven Sprocket Support (95)
?€¢
Leaking seal rings

?€¢
Porosity, damage, misalignment

Channel Plate and Gasket, and Valve Body, Gaskets, and Channel Plate
Porosity, fluid leak across the channels, misalignment, damage, or fluid restriction
Low and Reverse Band and Servo
No apply or slipping
Servo Piston (69)
Broken or binding
Servo Piston Seals (71, 72)
Leaking
Servo Pin (67) and Springs (66, 68)
Binding
Servo Cover (73)
Broken, loose, or leaking
Low and Reverse Band (111)
Broken, worn, or out of position
Anchor Pin (64)
Broken
Fluid Feed Tubes (83)
?€¢
Broken, bent, or plugged

?€¢
Missing or leaking seal rings

Transmission Case (1)
Porosity, fluid leak, or restriction
Shift Linkage
Disconnected or misaligned
Manual Valve (800) and Link (802)
Disconnected or misaligned
#1 Checkball
Missing, no low band fluid
Fluid Level
Low
Fluid Pressure
Low
Refer to High or Low Line Pressure .
Most likely your trans needs to be rebuilt !
to

You'll have to go to GM for this diagram, but sounds like it's just dirt plugged the movement of fluid to reverse clutch pack. Since Google is your friend, type in "fluid path diagram for a GM TH400 transmission" and see what comes up.

1. Check the fluid level. The first thing to check if you suspect that the transmission is acting up is the automatic transmission fluid (ATF) level in the transmission itself. The dipstick on the TH400 can be found inside the engine bay, on the passenger side toward the firewall (opposite the radiator). Pull the handle attached to the dipstick, which will remove it from the dipstick tube. Clean any fluid off and put it back into place, making sure that it seats all the way. Then remove it again and look at the tip of the stick. There are level indicators there, which will tell you if the transmission is low on ATF.
   

2. 2

   Check the linkages. The linkages that are connected to the shift lever can get out of alignment at times, causing sloppy or difficult shifter response. Look for abnormalities such as bent or broken parts, loose attachment points, or blockages that would prevent smooth shifting.
   

3. 3

   Change the filter. Unbolt all 13 transmission pan bolts (on the bottom of the TH400) and remove the pan. The filter is found in this area of the transmission. Filter kits, which include the filter and a new pan gasket, can be found at any auto parts store. Replace the filter and fill the transmission with new ATF (the TH400 requires six quarts). Do not put the bolts back on too tightly, as the gasket can become damaged. Six to 8 foot-pounds should be plenty. If no torque-wrench is available, just put them on as tight as you can by hand, and then turn them 1/2 revolution.
   

4. 4

   Inspect the cooler lines. The number-one killer of automatic transmissions is heat. If the cooler lines that come from the radiator are damaged or leaking, it might be necessary to replace them. These items can also be found at the local parts store.
   

Hi Sandra:
Normally if oil or transmission fluid mixes with coolant it will turn milky looking like a milkshake. Your leak must be pretty fresh. from your description that it is coming out of the coolant overflow I am thinking you have a radiator transmission cooler leaking into the cooling system.

You will need a new radiator and possibly all the coolant hoses if they have become soft from the transmission fluid.

In most cases if your getting transmission fluid in the radiator it is cause by a bad transmission cooler that is built into the radiator and the fix is to replace the radiator.

The repair will change in price from where the leak is coming from. If the pan is leaking or the rear seal your looking at $100.00 or less. If the front seal is leaking then around $550.00. The most common leak is the pan gasket. Also if the transmission fluid and filter have not been replaced in the last 30,000 miles and the pan is leaking then I suggest doing this also why the pan is off .

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Hi Sandra:
Normally if oil or transmission fluid mixes with coolant it will turn milky looking like a milkshake. Your leak must be pretty fresh. from your description that it is coming out of the coolant overflow I am thinking you have a radiator transmission cooler leaking into the cooling system.

You will need a new radiator and possibly all the coolant hoses if they have become soft from the transmission fluid.

In most cases if your getting transmission fluid in the radiator it is cause by a bad transmission cooler that is built into the radiator and the fix is to replace the radiator.

The repair will change in price from where the leak is coming from. If the pan is leaking or the rear seal your looking at $100.00 or less. If the front seal is leaking then around $550.00. The most common leak is the pan gasket. Also if the transmission fluid and filter have not been replaced in the last 30,000 miles and the pan is leaking then I suggest doing this also why the pan is off .

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

I'm guessing you mean transmission fluid poured out? That would certainly explain why it won't move. The most common leak point for older automatic transmission cars are the transmission cooler lines. They run from the radiator to the transmission (the cooler is built into the radiator) and they are made of steel so they are prone to rust. I would start looking there. The other leak points would be the lower pan, axle seals, and where the case bolts together. Take a look at the radiator and you should see some small steel lines bolted to the radiator. Follow them and look for heavy rust that is wet with fluid.

sounds like maybe transmission fluid leaking, power steering.

TRANSMISSION FLUID LEAKS,CAN BE FOUND AROUND PAN GASKET.CHECK PAN GASKET,IF IT LOOKS WET AND YOU SEE FLUID DRIPPING AROUND THE EDGE OF OIL PAN, REPLACE PAN GASKET, WHILE YOU REPLACING PAN GASKET REPLACE TRANSMISSION FILTER WHILE OIL PAN OFF.IF TRANSMISSION OIL PAN NOT LEAKING, CHECK TRANSMISSION OIL COOLER LINES GOING INTO RADIATOR YOU WILL LOOSE A LOT OF FLUID THERE ALSO TORQUE SHAFT SEAL WILL CAUSE HEAVY FLUID LEAK WHILE ENGINE RUNNING CHECK OIL COOLER LINES AND LOOK AT THE TORQUE AREA WHILE ENGINE RUNNING YOU WILL SEE FLUID POURING WHILE ENGINE RUNNING THE OIL PUMP PRESSURE WILL PUSH FLUID OUT AT THE LEAKING AREAS.