transmission low on fluid but I can't find a leak
 

2002 4x4 Blazer with 115,000 miles

here is the recent summary of whats going on...

A year ago the thermost broke and stuck closed. The engine overheated and I had to have it towed to the shop. They replaced the thermostat, hoses and radiator. They said the issues was becasue regular coolant was mixed with Dexcool (thank you Firestone).

Three months ago, I noticed that my transmission was not shifting very well. I checked the fluid and found that it was low, I added a qt or less to bring it up to the appropriate level. everyting seemed ok.

Two months ago, the intake manifold gasket blew. The coolant drained into the oil part of the block, it overheated, shut down etc. Had it towed to the shop they replaced the gasket, drained the block, replaced the thermostat. Not sure if they disconnected any lines to the radiator at that time.

last week I again began to think that my transmission was not shifting correctly. Yesterday I checked the fluid and found that it was low, I added 3/4 qt to bring it up to the appropriate level. everyting seems ok again.

I see no visible sign of a fluid leak, and not puddles under the car. Where could the fluid be going or leaking from? Is it possible that fluid is leaking out around front CV joint/axle assmbly? I know these are pretty worn and need to be replaced, the boots have grease or fuild on them could it be the leaking trans fluid? Could the fluid be leaking out only when I drive hence the fluid is on the road where I can't see it?

The last time I had the transmission flushed was at 50,000. I don't know if the trans filter has ever been changed. Should I have the filter and fluid changed?

What would you recommend as my next actions?

Check the level in your transfer case. Pull the upper plug and if oil comes pouring out you will know where your tranny oil is going. If so, you've got a seal or two to relpace.

how serious of an issue is it to have Transmission fluid in the transfer case.

The transfer case uses ATF. So nothing will be hurt. But after enough leaks in it will start blowing out the vent if that is the issue. But if they replaced the radiator did you ask if they added an trans fluid? If it was me I would check the transfer case first if that is OK. I would top off the trans when warm. Then watch it & hope for no more repairs.