I think this question is best answered by the Rov who led the Kehila of Torah Im Derech Eretz in America. Who can be a better authority than he. That, of course, is HaGaon HaRav Shimon Schwab ZT”L, Rav of the Torah Im Derech Eretz Congregation Adas Jeshurun in Washington Heights, the congregation started by TIDE founder HaGaon HaRav Samson Raphael Hirsch ZT’L:
“However, in addition to the legitimate shitos we have discussed, there is yet another, more modern version in vogue called “Torah Umaada”. Apparently this is identical with Torah Im Derech Eretz, especially since both claim a belief in the priority of Torah over maada. Both seems exactly alike, but like two left gloves which cannot be worn together, they don’t fit! . . .
“Rav Hirsch ZT’L has inscribed two emblems on his banner. One is Torah Im Derech Eretz and the other is the so-called “Austritt”, which means severance, or total and non-recognition of any type of institutionalized heresy, “minus” or apikursus. This is also a resolution not to contribute, participate in, or support any cause which accords validity to the disbelief in Hashem or to the denial of the authenticity of Torah shebiksav or Torah shebaal peh. In other words, “Austritt” states that the Torah is our sovereign ruler, and it makes us independent of all those who deny its Divine origin…
“To summarize, Torah im derech eretz without Austritt is considered treif l’chol hadeios! Even if you call it Torah Umaada.”
(Selected Essays pp.160-162)