I don't think that transmission coolers are that necessary. If you do a lot of towing or put stress on it, just check the oil more often. Smell it, and if it smells burned, like it is getting hot, then replace the oil. Proper maintanence is always cheaper than the improper type.

Mike
_________________________
'If a man speaks obscurely when he could speak more clearly, his words are to be interpreted against himself.' - Martin Luther