Rear freeze plug

A small coolant leak can travel a long way along seams and edges before falling and they often aren't easy to trace - adding a leak seeking dye to the coolant and searching with an ultraviolet light makes things much easier especially when access is difficult.

There is often a core plug (freeze plug) at the rear of cylinder heads and the rear of the block behind the flywheel/flexplate.

Sounds like a bad freeze plug. There's like 8 freeze plugs around the engine. 3 on each side and 2 in the rear between transmission. The only way to findout is by visually tracing the leak source.

Yes, you have to pull the transmission. But look it over closely. Most likely the coolant is coming from somewhere else. I have never seen or replaced a bad freeze plug back there. Water can't get to them to rust them out from the outside in. Only if you use water only to cool the engine. Heater hoses and the intake manifold gaskets can cause a leak in this area.

look for hoses with loose clamps you might have missed tightening on.

If you are in the cold freeze region then it can be FREEZE PLUGS or head gasket,

Freeze plugs prevent the coolant from cracking the block.

The only fix is to replace the freeze plugs.

Could be a freeze plug on the engine block. If you have a block heater installed in one of the freeze plug holes, check it for getting too loose and leaking. Pretty common problem with a block heater that's been in there a long time.

Are you in the North Eastern part of the US?
Is the engine clock in over 160,000+ miles?

The coolant leak is from the freeze plug(s) and / or head gasket.

The function of the freeze plug is protecting the engine block from cracking in extreme cold temperature. (below freezing point of coolant // -34F)
With the extend cold weather,the freeze plugs will pop out of the engine block.
If you coolant mixture ratio is below 50/50 then the coolant will freeze and expand well above -34F

You can see example for the leaky freeze plugs HERE
==== Freeze plugs are hard to get to and it's labor intensive to replace.
You MUST replace all freeze plugs before you start the engine.
Low or no coolant will over heat the cylinder head and damage the head gasket. ====
A radiator shop will able to do a compression test on the cooling system.
Coolant is toxic to pets! Please do your best to clean up general area and inspect the source of the leak.

More then likely could be a rear engine block freeze plug, transmission will have to be remove, to replace freeze plug.

No, that would probably be a freeze plug on the back of the block if the coolant is coming out between transmission bell housing and engine.

Have you checked to see if a freeze plug came out of the engine?