Hey Smoke - cold you give us a few more specifics?

Several things. In a "standard" configuration say in a 3/4 ton GM pickup pulling a 5,000 pound trailer it is not out of the ordinary to see the fluid in the 180-200 degree range in "Drive" - it may go to 225 degrees on an uphill pull. If the truck was purchased with a "trailer-tow" package that includes an external transmission cooler, the fluid would be typically 170-185 degrees under most all conditions.

In a car, say a Chevelle or Impala size - the temperature should be in the 170-185 degree range at most times.

If these temperatures can not be maintained, there may not be enough cooling capacity. Prolonged temperatures above 190 can cause damage - especially to stock soft parts.

Is yours a "stock" configuration?

If you have lots of foam - that's a bad sign and you are absolutely correct, it does not remove heat nearly as well as fluid.

Is this a recent problem? If so, are you sure that the fluid is clean, of the correct type and at the proper level as determined by the dipstick - checking warm in "Park" or "Neutral" with engine running (please be careful as even at it's normal temperature the fluid is very hot and will burn if it squirts out of the dipstick tube!)

If this is a new or transplant unit, you may need additional cooling. I'm a fan of another radiator unit but a deeper, finned pan may fit your application as long as you remember you now have a new "low spot" under the car and don't try and straddle any big rocks!

Other will chime in - but this may get the creative juices flowing.

Regards,
Glenn